Strands Of Connective Tissue Research Articles

“Acoustic Neuroma”: Comparison of traumatic and neoplastic

An eighth nerve traumatic neuroma was found in the vestibule of the inner ear one year after labyrinthectomy. It consisted of myelinated and unmyelinated nerve fibers twisted together among a few strands of connective tissue. Myelin sheaths of about twenty layers were formed by typical-appearing Schwann cells. An ordinary “acoustic neuroma” was compared with it by light and electron microscopy. Its cells contained numerous fine fibers and abundant rough-surfaced endoplasmic reticulum. They produced collagen fibers and myelin figures. Basement membranes and cross-banded figures were observed and lead us to regard the cells as Schwann cells rather than fibroblasts. “Schwannoma” seems to be the best name for this type of tumor.

CEREBRAL INTERVASCULAR STRANDS OF CONNECTIVE TISSUE AS ROUTES OF TRANSPORTATION.

AbstractIn the facial nucleus of the rabbit, fixed by a procedure of perfusion with delayed autopsy, intervascular strands of connective tissue contain on rare occasions either minute red PAS‐stained granules or clear vacuoles. With increasing age, the strands are transformed into homogeneous connective tissue bands.On the basis of these microscopic observations, it is inferred that, in younger animals, soluble and insoluble products can be channeled via the intervascular strands to adjacent blood vessels.

The fine structure of crustacean proprioceptors. II. The thoracico-coxal organs in Carcinus, Pagurus and Astacus

There is a complex of proprioceptor organs spanning the thoracico-coxal joints of the walking legs of decapod Crustacea. The muscular receptor is a specialized portion of the promotor muscle of the leg, associated with sensory fibres which are the dendrites of neuron-like sensory cells. Similar sensory fibres enter strands of connective tissue which are attached distally with the levator and depressor muscles of the basipodite (innervated elastic strands). In macrurans, but not in crabs, there is in addition a thoracico-coxal chordotonal organ. The fine structure of these proprioceptors is described, in Carcinus , Pagurus and Astacus . In Carcinus and in Pagurus the dendrites of all the sensory fibres are associated with specialized strings of connective tissue, within larger connective tissue strands. Fine processes of the dendrites (dendrite fingers) penetrate these connective tissue strings (vacuolated strings) and run up and down them for a certain distance, within the extracellular connective tissue substance, which is amorphous connective tissue containing bundles of collagen fibres. Elsewhere the dendrites are surrounded by sheath cells. The connective tissue of the strands consists mostly of collagen, except proximally in the muscular receptor, where amorphous connective tissue is more plentiful. Blood channels penetrate the strands in places. Appearances which seem to be connected with the formation of the amorphous connective tissue are described. In Carcinus and in Pagurus three sensory fibres are associated with the muscular receptor; these are referred to as T, S and P . The dendrites of T are associated with vacuolated connective tissue strings which attach directly to the proximal ends of the fibres of the proprioceptor muscle. The S dendrites pass into strands of connective tissue flanking the muscle; dendrite fingers of P , which is a smaller nerve fibre, enter some of the vacuolated strings which are associated with the S dendrites. The elastic strands are innervated each by one or more sensory fibres, with dendrites again associated with vacuolated connective tissue strings. In Astacus two sensory fibres send irregularly branched dendrites into a strand of connective tissue proximal to the proprioceptor muscle. No specialized connective tissue strings can be distinguished, but there are unsheathed dendrite fingers penetrating the connective tissue in places. The chordotonal organ contains isodynal scolopidia, each with two bipolar sensory cells of similar fine structure. A rough calculation of the surface area of the dendrite fingers of the S neuron of Carcinus has been made.

Connective tissue membranes and their apparent role in transporting neurosecretory and other secretory products in insects

Circumstantial evidence is presented, in the fly, for the direct transport of secretory products from secretory cells to cells of target organs, by way of continuous connective-tissue membranes. Secretory material passes to the periphery of the secreting cell and accumulates in channels within the basement membrane. The channels converge and pass along connective tissue strands, or may pass directly, into channels within the sheath of the target organ; there they diverge, in some cases opening into a system of interconnecting channels. Organs for which such a system is described include the ring gland complex, the larval lateral and dorsal nerves, the recurrent nerve to the larval gut, stretch receptor-type organs, pericardial cells, ventral nephrocytes, and oenocytes. Secretion-filled channels have further been found within the basement membrane overlying the imaginal buds in the prepupal stage; channels within the basement membrane of the leg rudiments and external genitalia have been traced to connective tissue strands originating from “stretch receptor-type organs”. These ultimately connect with the lateral segmental nerves and contain suspected secretory cells; such groups of cells could well be the source of origin of an intercellular agent regulating development, and the cells could thus function as regional “differentiation centers”. Electron microscope observations by other workers have suggested a close spatial relationship between the basement membranes and the various cellular membranes. Whereas the endoplasmic reticulum is possibly involved in intracellular electron transport, the basement membranes would here appear to be concerned in intercellular transport of cellular secretory products. It is suggested that the transport by way of basement membranes may also exist in groups other than insects.

Stretch Receptor-Like Organs in the Fly Larva: Their Possible Role in Growth Regulation

Typical insect stretch receptors and receptor-like organs present in larvae of Sarcophaga bullata and other flies contain associated cells which are suspected of passing secretory products into "target" organs by way of strands of connective tissue. In the fly larva, such organs are attached to leg rudiments, tracheal discs, muscles, the genital disc and gonads, and may be concerned with the neuroendocrine control of metamorphosis of these structures.

Factors Influencing Quality in Pork A. Histological Observationsa,b

SUMMARYSeventy‐eight carcasses of pigs, 4–42 months old, provided loins of varied intramuscular fat content. Developed experimental methods indicated that the fixation time and the staining processes of the longissimus dorsi muscle were dependent upon its structure and chemical properties. With an increase in maximum muscle fiber diameter, there was a decrease in the taste‐panel tenderness scores on the cooked longissimus dorsi muscles. There were no significant relations between tenderness measurements and total amount of connective tissue; however, the coarseness of the collagenic connective tissue strands was inversely related to the tenderness of the longissimus dorsi muscle.

The sensory neurones and sensilla in the abdomen and thorax of the blowfly larva

ABSTRACT The peripheral nervous system in the Phormia larva consists of bipolar neurones that end in specialized sensilla, and bipolar or multipolar neurones with ramifying distal processes. The former are associated with the cuticular sensilla and chordotonal organs. The latter (a) constitute a sub-epidermal nerve-plexus with processes that occasionally run over skeletal muscles, (b) innervate specifically orientated strands of connective tissue, the longitudinal, vertical, and ventral stretch receptors, and (c) innervate the tracheal epithelium, imaginai buds and associated pedicels, and the nerve-sheaths.

An electron microscope study of an abdominal stretch receptor of the cockroach

The longitudinal stretch receptor of the cockroach ( Blaberus) consists of a single multipolar neuron associated with a strand of connective tissue. Schwann cells invest the axon, cell body, and dendrites. The terminal regions of the dendrites are naked and embedded in the connective tissue matrix. There are no connexions between the naked sensory endings and the collagen-like connective tissue fibrils. Mitochondria are the only prominent cytoplasmic inclusion in the dendritic terminations. The ultrastructure is compared with that of vertebrate and invertebrate mechanoreceptors and correlated with electrophysiological data.

The fine structure of crustacean proprioceptors I. The chordotonal organs in the legs of the shore crab, Carcinus maenas

In the walking legs of the shore crab, Carcinus maenas , is a series of chordotonal organs. Each organ consists of a strand of elastic connective tissue in which are embedded scolopidia. The anatomy and histology of the organs in the coxopodite-basipodite, meropodite-carpopodite, carpopodite-propodite and propodite-dactylopodite joints are described in detail, as seen by light and electron microscopy. The organs are hereafter referred to by the initial letters of the leg segments with which they are associated. The CB organ runs from a projection near the dorsal hinge of the coxa to the dorsal rim of the basipodite. MC1 runs from the side of the tendon of the ‘accessory flexor’ muscle to two attachments on the preaxial wall of the meropodite. MC2 runs from the adductor tendon to the preaxial wall of the carpopodite. CP1 runs from the productor tendon to two ventral attachments on the carpopodite. CP2 runs from the reductor tendon to the floor of the propodite. PD runs from the adductor tendon to the postaxial wall of the dactylopodite. The scolopidia have a tube distal to the scolopale, into which are inserted the ends of the distal processes of bipolar sensory nerve cells. The tube is an extracellular organ apparently formed by the cell that contains the scolopale as an intracellular organ. Each scolopidium has associated with it two sensory cells, whose cell bodies lie in, on or near the connective tissue strands. In CB the sensory cells of a pair are similar to one another (isodynal scolopidia); in the other organs the two cells are dissimilar in their fine structure (heterodynal scolopidia). The difference, in the heterodynal scolopidia, consists in the presence or absence of a part of the distal process, the ciliary segment, which has nine double peripheral filaments regularly spaced, and in the precise form of the distal end of the axial filament. In all scolopidia, the two distal processes of the sensory cells are separated by intrusions of the sheath cells or of the scolopale cell, except for an area near the base of the scolopale where their cell membranes are in apposition; this area is referred to as the ephapse. At the level of the base of the scolopale the distal processes each contain an axial filament, which shows transverse striations, and there are attachment plaques between the distal processes and the scolopale cell. Distal to this level, each sensory cell contains a centrosome. Distal to the centrosome, the distal processes, which cross the scolopale space to end in the tube, can be divided into the following regions: a ciliary segment (where it occurs), a paraciliary segment characterized by nine double peripheral filaments less regularly arranged than in the ciliary segment, and a terminal segment characterized by numerous single microtubules. It is suggested that in each scolopidium one sensory cell responds to extension of the strand, and one to its shortening. This might account for the unidirectional responses observed in the organs. No structural basis for the observed differentiation of the sensory cells into ‘position’ and ‘movement’ receptors could be found.

The surgical considerations of bullous emphysema.

Increasing surgical interest in bullous emphysema has been manifest in recent years. Justification for surgery in many series of cases has been vague but there is more and more agreement on the necessity for considering an increasing number of these patients for surgery. The first American reference on this subject was in 1925 when Koontz reviewed the literature and collected 105 cases. The surgical program was somewhat vague at this early date due to the undeveloped status of resection surgery. By 1937, Schenck had collected 381 cases and presented five of his own. Of these, four were subjected to local excision and one was lobectomized. He remarked that cysts easily herniated from the wound facilitating excision. In fact, he stated that bullae might continue to increase in size with each breath, necessitating opening them to facilitate dissection. Tyson, in discussing this presentation, emphasized the short life expectancy in many of these patients and related a case operated 11 years previously who expired with cor pulmonale. In 1949, Ravitch and Hardy reported 12 patients and advised surgery as soon as the condition was diagnosed. Ten of their patients underwent lobectomy and one pneumonectomy. This was apparently the ultraradical approach. By 1950, another group of 14 cases was reported by Samson and Dugan, and in 1952 Crenshaw and Rowles added 11 more. Both of these groups took a more conservative surgical approach, limiting the operation to local excision where possible and thereby conserving lung tissue. Many other significant contributions were made in the literature about this time, namely, Nissen, Head and Avery, Brock, Naclerio and Langer, Albritton and Templeton, and Massie and Weichon. The cause of bullous emphysema is not completely clear, but there appears to be a loss of elastic tissue in the lung. Certain predisposing causes may be present as a chronic cough, from repeated infections, spasm, or occupational hazards, or the condition may be secondary to chest wall changes. Many terms have been applied to the disease: blebs, bullae, tension cysts, air cysts, builous emphysema, pneumatocele, and “vanishing lung.” More important than the designation is the extent of involvement. This may not be fully apparent until lung function studies give some clue and actual thoracotomy reveals the true nature and extent of the process. Bullae may be uniloculated or multiloculated. They may be segmental in distribution or completely unanatomical in location. Frequently a group of pea sized blebs may be seen along fissure borders which is not discernible in roentgenograms. The capsule of the bulla is thin and translucent with many areas of fibrous thickening. On opening larger bullae, one sees many loose strands of connective tissue, lung substance and denuded vessels traversing the spaces. These may be so numerous and lacy as to resemble cotton candy, a term frequently applied to the diffuse category. Many bullae communicate with

Chordontonal organs in Crustace.

THERE is a series of proprioceptor organs in the joints of the walking legs of decapod Crustacea, each consisting of a strand of elastic connective tissue with which are associated bipolar sensory nerve cells. These organs have been mentioned by Alexandrowicz and Whitear1 and by Alexandrowicz2; work on their physiology has been published by Burke3, Wiersma and Boettiger4 and by Wiersma5. An electron microscope study of these organs in Carcinus maenas has now shown that they are chordotonal organs; the distal processes of the sensory cells are associated with scolopales.

A comparative study of intervascular connective tissue strands in the central nervous system.

Journal of Comparative NeurologyVolume 114, Issue 2 p. 189-208 Article A comparative study of intervascular connective tissue strands in the central nervous system Jan Cammermeyer, Jan Cammermeyer Laboratory of Neuroanatomical Sciences, National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Public Health Service, Bethesda, MarylandSearch for more papers by this author Jan Cammermeyer, Jan Cammermeyer Laboratory of Neuroanatomical Sciences, National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Public Health Service, Bethesda, MarylandSearch for more papers by this author First published: April 1960 https://doi.org/10.1002/cne.901140206Citations: 24AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume114, Issue2April 1960Pages 189-208 RelatedInformation

Further Observations on Proprioceptors in Crustacea and a Hypothesis About Their Function

In the coxal region ofEupagurus bernardusthe following receptor organs have been found: (1) a muscular receptor spanning the thoracico-coxal articulation, its innervation, in which several neurons take part, being arranged on a similar pattern as inCarcinus; (2) two innervated elastic strands running along the bundles of mm. levator and depressor basipoditis respectively and inserting into the tendons of these muscles; (3) a coxo-basipodite receptor consisting of connective tissue strand with numerous bipolar nerve cells ending on it. With the exception of the coxo-basipodite receptor, all sensory neurons of these organs have their cell bodies located in the central nervous system.It is suggested that these receptors convey impulses elicited by the movements of the legs and some hypotheses concerning the role of each of them are put forward.

The structure and function of abdominal stretch receptors in insects.

The morphology of dorsal abdominal stretch receptors in representatives of the Orthoptera, Odonata, Hymenoptera and Lepidoptera is described on the basis of dissections, serial sections and whole mounts. The receptors consist of sensory neurons in association with connective tissue strands or muscles. The organs are found to be slung between the intersegmental folds (Lepidoptera), between one intersegmental fold and the dorsal body wall (Orthoptera, Odonata, Hymenoptera), or between the dorsal body wall and a nerve branch in the abdomen (Odonata). The mode of anchorage of the organs and other morphological features suggests a proprioceptive function. This can be demonstrated by oscillographic recording from the axons of the sensory neurons. An apparatus is described in which isolated preparations containing the receptors could be subjected to mechanical stimulation by stretch of controlled intensity. Over a certain range the frequency of impulse discharge from the sensory neuron is linearly proportional to the tension applied to the receptor. Adaptation is slow, and the organs in all insects investigated behave similarly and in a way typical for static receptors. Three pairs of receptors per segment are present in the Odonata (dragonfly larva), and an attempt is made to correlate their responses with the chief abdominal movements of the insect. In comparing the anatomical features of the various receptor organs, it is pointed out how they can be arranged in a series leading from neurons closely associated with the body wall, to those specialized to register stresses in connective tissue strands which are slung between suitably placed points in the segment, and finally to sensory neurons in closer association with the abdominal musculature. The series culminates in the lepidopteran receptor which shows striking points of resemblance to the vertebrate muscle spindle.

Calcifying epithelioma of malherbe in the dog: A pseudoparotid tumor

B of its relative rarity in the human being and its heretofore unreported occurrence in the dog, and because this lesion may entail a diagnostic pitfall, we felt that this report might be of more than routine interest. Calcifying epithelioma in man is manifest usually in the second or third decade as a hard, solitary, rounded tumor situated deep in the subcutaneous tissues. It is covered by normal uninvolved skin and is freely movable with it. It may attain considerable size; tumors 5 cm. in diameter have been observed. It is usually found in the upper extremities, face, neck, or back, well demarcated from the surrounding structures of the deep corium or subcutaneous fat by a well-developed capsule of collagenic connective tissue. The histologic appearance is quite characteristic for this tumor. Irregularshaped masses of epithelial cells are separated from one another by thin strands of fibrous connective tissue. The epithelial cells are of two kinds, a germinative or basal-cell type and a “shadow cell” that occurs in sheets. There is marked similarity in the appearance of the basal cells and those of basal-cell cpithelioma, and this erroneous diagnosis may be made if sufficient care is not exercised. The basophilic cells are rounded or elliptical and composed of nearly all nucleus, the cytoplasm being quite scant.? The “shadow cells” are pale eosinophilic masses of epithelial cells that have lost their nuclear hematoxylinophilic property but not their individuality. One can often see areas of transition between the two cell forms. Sheets of cornified cells can be found either in the basophilic cellular masses or in the “ shadow cells. ” These keratinized nests arc prone to undergo calcification. The stroma quite frequently manifests a number of foreign body giant cells either near the pale cosinophilia “shadow cells” or near an area of hemorrhage, both of which were observed in the case to be described. Occasionally bone may be found in the connective tissue strands or in areas where calcification has previously occurred. There are many theories of histogenesis : calcification of a sebaceous gland epithelioma,l misplaced cpithelial rests of sebaceous glands,= degenerating basal-cell carcinoma,3 hair matrix cells,4’ 5 and primary epithelial germ cells.G

Macular changes after venous obstruction.

At least four mechanisms of branch or central retinal vein obstruction are known. 1 They are (1) venous endothelial proliferation, (2) periphlebitis leading to obstruction, (3) stagnation thrombosis, and (4) pressure from without as in branch arteriovenous nicking or central thickening of the intermediate connective tissue strand at the lamina cribrosa. The usual clinical picture which initially follows the obstruction is too well known to require description. It suffices to say that this is the clinical picture usually erroneously called venous branch or central vein thrombosis. In view of recent work 1 showing the small part actually played by thrombosis in this syndrome, branch venous or central vein obstruction would be a much more accurate term to use. Verhoeff's original fight for this contention should be noted. 2 The myriad fundus changes seen six months to many years after branch or central retinal vein obstruction have been neglected both clinically and

The anatomy and histology of the sacrouterine ligaments

To determine the gross and microscopic anatomy of the sacrouterine ligaments as well as their physiology and clinical significance, a review of the literature and an anatomical study were undertaken. Many articles refer to these ligaments, but little specific work has been done on them. Mainly they are mentioned secondarily as uterine supports or pertaining to the correction of uterine malposition. The studies which have previously been done leave the nature of these ligaments in a confused and controversial status. However, from the literature it may be concluded that the main supportive structures of the uterus are the parametrial and paravaginal musculofascial tissues, and that the sacrouterine ligaments are secondary in supportive action. Functionally the sacrouterine ligaments act to hold the cervix upward and posteriorly. Clinically these ligaments may be helpful in a differential diagnostic respect as well as being involved in certain pathological processes. Various surgical procedures have been directed toward these structures, some primary and others secondary to other procedures in the pelvis.An attempt was made to determine the actual anatomical configuration and histological components of the sacrouterine ligaments. To do this the pelves of thirty-three cadavers were studied. Ten of these were partially preserved dissecting laboratory specimens while the remainder were autopsy material. Thorough dissections of the ligaments and their contained structures were carried out in five cases. Drawings were made of each case: first, before the pelvic organs were disturbed, and second, after the sacrouterine ligaments were placed under tension. The entire ligaments or blocks thereof were removed for microscopic examination in twelve cases, and various staining techniques were utilized to demonstrate the tissue components.To summarize the gross and microscopic anatomy of the sacrouterine ligaments it may be said that they are bands of tissue coursing from the cervix around the inlet of the pouch of Douglas to become attached to the sacrum. Grossly they are often merely potential ligamentous structures. Histologically they may be divided into thirds. The anterior or cervical third contains in order of prominence (Table III) smooth muscle, fibroelastic connective tissue, blood vessels, nerves, and lymphatics. The intermediate third is made up of IIIHistological components of the sacrouterine ligaments in order of thier prominenceHistological Components by RegionsCervical (Anterior third)Smooth muscleConnective tissueBlood vesselsNerves (Sympathetics and parasympathetics)LymphaticsIntermediate (Middle third)Dense connective tissue (stratum fibrosum)Loose connective tissue and fatNerves and ganglia (parasympathetic)Blood vesselsSmooth muscleLymphaticsSacral (Posterior third)Loose connective tissue and fatBlood vesselsNerves and lymphatics connective tissue concentrated in a subserosal stratum fibrosum and scattered in the deeper zone as a less dense meshwork. Nerve elements are numerous and blood vessels are moderately prominent. There are also a few scattered strands of smooth muscle in this region, and lymphatics may be present to a variable extent. The posterior or sacral third is composed almost entirely of loose strands of connective tissue and intermingling fat. There are a few vessels, nerves, and lymphatics located here.There is no reason why, if the sacrouterine ligaments are well developed, they should not be utilized in such operations as vaginal hysterectomy, enterocele correction, uterine retroversion, and prolapse; but they should not be credited with undue supportive value. The anterior or uterine end of the ligament may be, and often is, well developed. This has led to the opinion that these ligaments have more supportive action than this study would appear to justify, due to the weak and insignificant development of the posterior aspect. The old addage that a chain is no stronger than its weakest link can aptly be applied here, for the supportive action of the posterior third of the ligament is certainly questionable.

Studies of the Physiology and Toxicology of Blowflies

Lucilia cuprina larvae possess two pairs of malpighian tubules. One pair,having a yellow appearance, is restricted to the posterior end of the body.The other pair commences at the posterior end of the body and rims forwardsas far as the brain and then backwards on either side of the gut to enter itby a common duct. Whereas the ascending regions are greatly enlarged andhave a white appearance caused by many small spherical granules in thelumen, the descending regions� have the usual yellow appearance. The tubulesare held in place at several points by fine strands of connective tissue.

The Structure and Development of the Segmental Excretory Organs of Asellus aquaticus (Linné)

1. The maxillary organ (‘gland’) of Asellus is pyramidal in form and consists of an end sac in the form of an inverted V placed transversely to the body, a duct describing four vertical loops, one anterior and three posterior to the end sac, and a chitin-lined exit-tube leading from the duct to the exterior and enlarging along its course into a bladder. A sphincter consisting of four cells with two sets of intracellular fibrils controls the aperture from end sac into duct. The external aperture is on the medio-posterior face of the limb-base. The organ is anchored to various points on the exoskeleton by connective tissue strands. The spaces among the coils are partly filled by cells which accumulate reserve materials but leave channels for the circulation of blood. Histologically the organ resembles those of other Crustacea in all essentials. 2. The exit-tube is ectodermal, the rest of the organ mesodermal. Duct and end sac originate from independent rudiments, the former from a single large cell (? nephroblast) located where the medial wall of the maxilla joins the body, the end sac from a number of smaller, scattered cells dorso-laterally to the duct rudiment. Duct and end sac are probably derived from the second and third mesodermal teloblasts respectively. The sphincter originates from the end sac. Cells of the genital rudiment are associated with the end sac in early stages. 3. There is considerable evidence that the segmental excretory organs are homologous throughout the Crustacea. 4. They differ from the coelomoducts of other Arthropods and of other phyla in having a composite structure. 5. This suggests that the duct may be homologous with the nephridia of other groups of animals. There is functional and morphological evidence for this but nephridia are typically ectodermal in origin, so that if they are homologous there must have been a movement of the presumptive nephridioderm, during the evolution of the Crustacea, from the ectoderm to the mesoderm. 6. The antennal organ ofAsellus (Némée's gland) consists of a compact group of five large cells containing intracellular vacuoles. It is suspended in the body cavity by connective tissue strands, and has no external opening. A nerve supplies it from the antennal ganglion. In the adult it appears to be an organ of internal secretion: the vacuoles have been seen in the distended and in the exhausted phases. 7. Néméc's gland originates close to the epidermis at the antennal-mandibular intersegment. It appears to be mesodermal and probably represents the duct of the typical segmental organ (not the end sac). 8. Ter-Poghossian's organ, consisting of a large number of small cells in a compact group attached to the ventral epidermis, median and anterior to Nemec's gland, has no other anatomical relations. It appears to be ectodermal in origin. 9. The ‘rosette’ glands resemble structurally the tegumental glands of Decapods. The gland cells appear to be mesodermal, but the origin of the central duct cell was not determined. 10. Gastrulation in Asellus is essentially similar to the process in other Malacostraca, but it seems possible that the distinction between naupliar and post-naupliar regions is not so sharp as has usually been maintained. 11. The value of the embryological evidence concerning the homology of the parts of the second maxilla is considered. It does not entirely agree with interpretations based on adult morphology.

The development in vitro of the mammalian gonad. Ovary and ovogenesis

Several investigators have tried to cultivate in vitro the mammalian and avian gonad, usually with the object of obtaining the growth and differentiation of the germ cells under in vitro conditions. The results so far obtained, however, have been disappointing. Champy (1920) is the only author, so far as we know, who has definitely claimed to observe some differentiation of the germ cells in vitro . He states that in testicular explants from the mature rabbit he observed the transformation of spermatogonia into spermatocytes, but the process did not advance beyond the leptotene phase of meiosis. Champy’s findings, however, have not been confirmed by other investigators, probably owing to the difficulty of cultivating mature testicular tissue. In birds, progressive differentiation of the germ cells in vitro has not been recorded. Cultures of ovarian and testicular tissue of the embryonic fowl have been studied by Fano and Garofolini (1927 and 1928). The explants formed an epithelial outgrowth which was soon replaced by what appeared to be fibroblasts. Dantchakoff (1932) cultivated the undifferentiated gonad of 3½-day fowl embryos and described three types of cells in her cultures: ( a ) large amoeboid cells—Waldeyer’s “Ureier” or “Urkeimzellen”—which in vitro developed pseudopodia and showed active amoeboid movement, ( b ) connective tissue strands, ( c ) epithelium ­ like tissue. Wermel (1933) made cultures of the undifferentiated gonad and of embryonic and adult testes and observed growth of both the somatic and germinal tissue. Muratori (1935 and 1937) cultivated gonad tissue from embryonic and newly hatched fowls, but although he describes the nuclear pattern of the germ cells emigrating from the explants, he makes no mention of any differentiation occurring in the explanted gonocytes. Several workers have grown mammalian gonad tissue in vitro .