Variation In Total Length Research Articles

Trypanosoma lewisi infections in normal rats and in rats treated with dexamethasone.

SYNOPSIS. Administration of dexamethasone to rats infected with Trypanosoma lewisi resulted in the development of exceedingly large populations of trypanosomes which were fatal to their hosts. The elevated levels of parasitemia in treated rats early in infections were thought not to be a result of an increased reproductive rate. However, trypanosomes in treated rats 2 days postinfection did have a higher coefficient of variation in total length and a greater percentage of dividing forms than those observed from infected rats which were not given the drug. The course of infection may be markedly altered not only in intensity but also in length by this corticosteroid. It is suggested that dexamethasone administered at the levels recorded to rats infected with T. lewisi inhibits the production of ablastin and trypanocidal antibodies.

COMPARATIVE STUDY OF DITYLENCHUS DESTRUCTOR THORNE, 1945 (NEMATODA:TYLENCHIDAE), FROM POTATO, BULBOUS IRIS, AND DAHLIA, WITH A DISCUSSION OF DE MAN'S RATIOS

Nematodes having the general characters of Ditylenchus destructor Thorne, 1945, from the potato, bulbous iris, and dahlia, did not reveal any significant difference in the basic structures to suggest the presence of more than one species. However, due to host influence, there may be some variation in total length, width, number and arrangement of sex cells, length of oesophagus, length of spear, and tail shape. Nematodes from potato were successfully transferred to dahlia and carrot, and from iris and dahlia to potato.Specimens of D. destructor from potato interbreed freely with specimens from bulbous iris and from dahlia. Evidently these nematodes from the three hosts are the same species, i.e., D. destructor.Among the ratios used, the values of c in the case of males and that of "V%" have some support from the data.

The Colon in the Healthy Newborn Infant

In spite of the rarity of roentgen examinations of the colon of the newborn infant in routine practice, it is necessary for the radiologist to have a well founded knowledge of the appearance of the normal colon at this and subsequent ages. This paper presents the roentgen findings on barium enema study of the colon in a group of 105 healthy newborn infants, of whom 51 were white and 54 colored. Fifty-three were boys and 52 girls. None of these babies had any gastro-intestinal disturbances. They were, with 6 exceptions, full-term children, varying in age from two to eight days. The smallest infant weighed at birth 2,385 grams; the largest, 4,755 grams. Two of the mothers had positive tests for syphilis. The remainder were serologically negative. The infant is even less co-operative than some of our adult patients. Consequently, one must have at hand a simple but satisfactory method for examining the large bowel. After an opaque meal has been given, barium can be seen entering the cecum and ascending colon in three to six hours, and in eight hours the entire colon may be visualized (6). Distribution of the meal throughout the colon, however, is so scattered that a satisfactory view is rarely obtained. Not only is it difficult at times to distinguish between ileum and large bowel, but in one infant the meal may have only entered the cecum in eight hours, while in another evacuation of the head of the barium column may have occurred. This may necessitate roentgen study at least at hourly intervals, and after all this work one may have adequate information only on colonic motility, and little or none on form and size. It is, therefore, evident that the colon is best examined by administration of a barium enema. Larimore made barium enema studies on 102 newborn babies, ranging in age from six and a half hours to thirty days (8). He found that frequently the right colon and the cecum could not be filled. Complete failure of the colon to fill was often encountered because of its intolerance to the enema. Larimore's work demonstrated variations in total length and regional topography of the infant's colon, analogous to those seen in the adult. Local redundancies and hyperrotation and descent of the cecum with increased total length of the right colon were observed. Bryant measured intestines removed at autopsy from 45 fetuses, 37 children, ranging in age from six months to seventeen years, and 160 adults (3). He concluded that the most striking characteristic of the human intestine is extreme variation in length, this variation averaging about 100 per cent. Variation in length, Bryant found, begins at or before the fifth month of intra-uterine existence and thereafter is evident throughout life in both the small and large bowel. The characteristic 100 per cent variation in length is present at birth as at all later periods of life.

RELATIONS BETWEEN TISSUE ORGANIZATION AND VEIN DISTRIBUTION IN DICOTYLEDON LEAVES

THIS PAPER deals with certain relations between leaf structure and the distribution of minor veins in the blade. In connection with work on the wound responses of foliage leaves the writer built up several series of slides which were equally favorable for the study of normal leaf tissues. It seemed from reviewing these preparations that vein spacing was often related to mesophyll organization. A careful analysis of leaves of three series of plants seemed to confirm this generalization and revealed a fairly close correlation between the photosynthetic and conductive tissue of the blade in these species. Several investigations have dealt quantitatively with the development of the minor venation in the leaf blade. Zalenski (1902), using leaves cleared in chloral hydrate and mounted in glycerin, called attention to variations in total length of vein per unit area in plants of given species even in similar habitats. This led to his later paper (1904), which is discussed at length by Maximov. He demonstrated a wide range in the structure of leaves distributed vertically along a single stem. On shrubby or herbaceous plants of moderate size he found leaves of higher insertion successively more xeromorphic with progressively greater vein length per unit area than those lower on the same stem. While this feature was associated with several other structural differences in the leaves investigated, he considered these vein specializations as most closely correlated with cell size in the different leaves. Schuster (1908) surveyed a considerable number of plants, giving attention to differences between sun and shade leaves. With few exceptions, shade leaves were larger than sun leaves of the same species, but the shaded leaves had reduced venation, in terms of total vein length per unit area of blade, compared with those in the sun. Benedict (1915) made an intensive vein study of a few plants but concerned himself particularly with ritis vulpina. He held that vein spacing (which he termed the vein-islet) for leaves of this species was correlated closely with the plant's age, diminishing regularly through successive years after the launching of a new plant from an embryo started by fertilization. His records were made photographically by transmitted light, using untreated living leaves, which method probably failed to record some of the lesser veinlets. While he noted the earlier work of Zalenski (1902), he does not include the very important paper by that writer published in 1904. Strain (1933) recently made a study of the types of vascular elements in the vein endings of a large number of species, by clearing whole leaves, cotyledons, and petals. He finds type patterns of tracheal organization rather than variations due to environ-

STUDIES ON THE VENOUS PULSE

This investigation comprises a study of venous pulse, carotid, cardiographic, and heart sound records from twenty-one men with normal hearts. The heart sounds were recorded by the method of Einthoven. When correction is made for transmission, the first heart sound begins, on an average, 0.131 of a second before the c-wave of the venous pulse, and has an average duration of 0.128 of a second. The second heart sound begins a few hundredths of a second before the v-wave and has a duration of 0.091 of a second. The third heart sound occurs shortly before or is coincident with the beginning of the h-wave. It has an average duration of about 0.03 of a second. Considerable variation from the average positions are noted in individual cases. This is especially true in the relation between the second heart sound and the v-wave. Measurements of the venous pulse and heart sound intervals show that the a-c, c-v, and v-h venous pulse intervals, the first to second and the second to third heart sound intervals, and systole tend to remain fairly constant in length when cardiac cycles of different length are considered. The v-a, h-a, and x-a venous pulse intervals, the third to first heart sound interval, and diastole tend to vary in length with variations in total length of the cycle. Records of the venous pulse and heart sound obtained from dogs show a similar relation to that found in man. The main difference observed was an earlier occurrence of the first heart sound before the c-wave of the venous pulse.