Dorsal Lamella Research Articles

Topical projection of the olivocerebellar system in the cat: an electrophysiological study.

AbstractUsing electrophysiological recording, topical aspects of the olivocerebellar projection were studied in the locally anesthetized cat immobilized with Flaxedil. Transcortical evoked potentials were recorded simultaneously from eight electrodes distributed over the cerebellar surface, and averaged with a LINC computer. Precautions were taken to eliminate virtual potentials from this volume conductor situation. The evoked potentials consisted of a 4–6 msec positive spike, latency 4.5–7 msec, followed by a 15–30 msec slow negative deflection. Each was recorded from one or two folia contralateral in distribution. Medial and dorsal accessory nuclei project largely to cerebellar vermis. A rostrocaudal relationship was found between posterior vermis and medial accessory nucleus, and vermal anterior lobe received its projection from the caudal and midportions of medial and dorsal accessory components. A dense representation of accessory nucleus responses was present over the declive as compared with other cerebellar areas. Paravermal responses of anterior lobe derived from rostral dorsal accessory olive, and principal olive connected to the hemispheral region. The ventral lamella of principal olive projected to Crus II, dorsal lamella to Crus I. These lobules are represented rostrally in the principal nucleus, whereas the source for paramedial lobules was situated more caudally. The results correlate well with the retrograde degeneration studies of Brodal ('40, '54) but differ in the detail of some projections.

The red nucleus and its efferent nervous pathways in the monkey.

AbstractA morphological study of the red nucleus and its efferent nervous pathways based on retrograde cellular degeneration (cell loss) and on degenerated fibers impregnated with osmic acid gave the folowing results. Interruption of the rubro‐tegmentospinal tract was associated with a complete disappearance of the cells in the contralateral magnocellular red nucleus and some cell loss in the adjoining tegmental gray. Interruption of the central tegmental bundle results in a complete cell loss in the parvicellular part of the ipsilateral red nucleus. Such a lesion is associated with degeneration of the rubro‐olivary fibers that terminate along the dorsal lamella of the ipsilateral principal olive. The interruption of the superior cerebellar peduncle does not lead to any cell loss in the red nuclei. The above findings suggest that in the monkey the red nucleus proper discharges exclusively downwards. The small‐celled part gives rise to fibers that travel in the ipsilateral central tegmental bundle and the large‐celled part gives rise to entirely crossed axons that descend in the rubro‐tegmentospinal tract. There apparently exist marked differences in the distribution of the nervous elements within the red nucleus and, correspondingly, in the origin of the efferent nervous pathways in the cat and in the monkey. The interruption of the rubro‐tegmentospinal tract does not lead per se to any noticeable motor impairment but appears to be an essential feature in the appearance of postural tremor and possibly in the production of other extrapyramidal signs in the monkey.

Dicranum leioneuron Kindb. New to the British Isles and Labrador, with a Description of the Sporophyte

Dicranum leioneuron Kindb.a little known, somewhat suboceanic moss is reported as new to the British Isles and Labrador and new localities are listed from Norway and Finland. Its sporophyte, not described before, compares more closely to that of D. bonjeanii De Not. than that of D. scoparium Hedw., but the differences are small. Attention is 1 Department of Botany, University of Helsinki, Finland. 2 Atlantic Regional Laboratory, National Research Council of Canada, Halifax, Nova Scotia. This content downloaded from 157.55.39.159 on Sun, 22 May 2016 04:57:08 UTC All use subject to http://about.jstor.org/terms 198 THE BRYOLOGIST [Volume 68 paid to the apparently poor development of the spores and capsules of D. leioneuron, although the reasons for this are not clear. Dicranum leioneuron Kindb. was first described from Nova Scotia and recently (Persson & Sjdrs 1960, Ahti & Isoviita 1962), in agreement with Tuomikoski's previous suggestion (unpublished), demonstrated to be identical with D. bonjeanii v. anotnalum C. Jens. and D. bonjeanii v. integrifolium Lindb. f. It represents an ecologically and morphologically well defined taxon which may be regarded as a distinct species. Dicranum leioneuron has been reported from Finland, Sweden, Norway, Denmark, Estonia, and Latvia in Europe as well as from Newfoundland, Nova Scotia, Quebec, and Ontario in North America (Ahti & Isoviita 1962). On an excursion to Ben Lawers, Scotland, during the Tenth International Botanical Congress in 1964, this poorly known moss species was found as apparently new to the British Isles by T. Ahti. It was also found on a number of places in Labrador during a surveying trip for peatmosses in 1963 by W. Maass. Its sporophyte was studied by P. Isoviita. Mr. T. Ulvinen and Dr. S. Eurola of the University of Oulu, Finland, have also kindly placed some new specimens at our disposal. Dicranum leioneuron resembles D. bonjeanii but the leaves are essentially nonrugose, somewhat shiny, slightly denticulate or entire at the apex, and the dorsal lamellae are absent or at most very poorly developed. The Scottish material is very robust and well developed, apparently because it was growing in pure patches free from strong competition with Sphagnum species, unlike the way that it is usually seen in Finland. Therefore the leaves are also unusually broad at base and less involute than indicated in our former paper on this species (Ahti & Isoviita 1962). The thick flagellary shoots that are extremely characteristic were absent or very poorly developed in the Scottish material. In cross section the cells in the upper lamina are rounded rather than irregularly quadratic or rectangular as in D. bonjeanii and D. scoparium, and the nerve contains a row of four guide cells.

Neurohaemal organs in crustaceans.

A NUMBER of structures of nervous origin in the higher Crustacea have recently been described under a variety of names, although they show a unity of structure and possibly of function. We wish to propose, tentatively, a common name to denote organs of this type in crustaceans, in order to avoid a needless multiplicity of names for organs which have many features in common. The organs are: the sinus gland of the eyestalk1,2; part of the pars distalis of the X-organ of the eyestalk3,4; the sinus plate or post-commissural organ of the tritocerebral region5; the pericardial organs of decapods6; the dorsal lamellae of the pericardium of Squilla and the associated system of dorsal trunks7; the transverse bar in the ventral blood sinus of the sixth thoracic segment of Squilla and the associated system of median connectives8; the apparatus nervi dorsalis cordis of the crayfish9; the neuropiles, or punctate substance, which extend over the ligaments of the heart in Palinurus and Scyllarus10.

ARTERIAL SUPPLY OF LATERAL PAROLIVARY AREA OF THE MEDULLA OBLONGATA IN MAN

Lesions of the lateral parolivary area of the medulla oblongata, such as occur in the syndromes described by Avellis,1Wallenberg,2Babinski and Nageotte3and Cestan and Chenais,4were after Wallenberg's5work generally regarded as due to occlusion of the posterior inferior cerebellar artery. Breuer and Marburg,6however, pointed out that similar lesions may be produced by thrombosis of the vertebral artery distal to the point of origin of the posterior inferior cerebellar artery or by that of the basilar artery, a fact which was confirmed by the extensive studies of Stopford.7In 1925 Foix, Hillemand and Schalit8described a new artery, the arteria fossae lateralis bulbi, and brought substantial evidence to demonstrate that most lesions of the lateral parolivary area (Ziehen9), including part of the dorsal lamella of the inferior olive and the descending root of the trigeminus nerve and its

Lestodiplosis alvei sp.n. (Diptera, Cecidomyidae)

Male. Length about 1·5 mm. Antennae slightly longer than head, thorax and abdomen: 2 + 12, basal enlargement of flagellar segments with regular ring of moderately long stout setae and one ring of circumfila, distal enlargement with two rings of circumfila and irregular ring of stout setae, loops of circumfila regular and moderately long, those on basal enlargement extending about one-third length of stem, distal ring on distal enlargement extending about two-thirds length of neck; 1st and 2nd flagellar segments fused; 3rd flagellar segment with stem about three times as long as broad, neck slightly longer, about three-and-a-half times as long as broad, distal end slightly darkened as on all flagellar segments; 10th flagellar segment with stem about four times as long as broad, neck slightly longer in proportion. Palpi quadriarticulate with few setae: proximal segment quadrate, 2nd just over three times as long as broad, 3rd about three times as long as broad, the same width as 2nd, distal segment about four times as long as broad, slightly narrower than two previous segments. Thorax brown. Wings hyaline; 3rd vein reaching margin at apex of wing. Legs hairy; claws moderately curved, simple; empodium slightly shorter than claws. Genitalia: basal clasp segment long narrow, small basal lobe prominent; distal clasp segment long narrow, darkened; dorsal lamella moderate length and breadth, distinctly longer than ventral lamella, deeply emarginate, each lobe rounded; ventral lamella comparatively short but broad; style long, moderately stout.