. Contributions to embryology. Embryology. Fig. 5.—Traosverse section of an cm ..1 —> ^imites, passing through one of the lower myotomes and the mesonephros, to show the position of the subintestinal artery and a chain of angioblasts which will form an artery of the mesonephros. The section is from a specimen of the same litter as the one shown on plate 1, figure 1, and from the same scries :ts figures 4 and 6. The level of the section is shown by a line on plate 1, figure 1. The section is 20 ii thick and is stained with hematoxylin and counterstaincd with orange G, cosin, and auran
. Contributions to embryology. Embryology. Fig. 5.—Traosverse section of an cm ..1 —> ^imites, passing through one of the lower myotomes and the mesonephros, to show the position of the subintestinal artery and a chain of angioblasts which will form an artery of the mesonephros. The section is from a specimen of the same litter as the one shown on plate 1, figure 1, and from the same scries :ts figures 4 and 6. The level of the section is shown by a line on plate 1, figure 1. The section is 20 ii thick and is stained with hematoxylin and counterstaincd with orange G, cosin, and aurantia. XUo. A. mes., a chain of angioblasts which connect the aorta with the v. cardinalis lateralis and which will form an artery of the mesencephalon but were not injected because they are still solid; A. si., a. subintestinalis; V. c. I., v. car- dinalis lateralis; V. c. p., v. cardinalis posterior. These angioblasts are mesial to the nephritic tissue. This section is, 1 think, similar to the .^^ection in Evans's hgurt^ 416 from a human embryo of the same stage, namely, with 23 somites, which shows the jiosterior cardinal ^•ein dorsal to the Wolffian duct Mild the lateral cardinal vein ven- tral to the duct. A comparison of text-figures 4 and 5 seems to me to indicate that the primary arteries of the nejihro- genic tissue are ventral to the ne- phrotome, but when the tubules are farther developed the artery crosses the neck of the tubule; in other words, the tubules grow ven- tral to the arteries. The study of the eml^ryo pig at the stage of 23 somites (as shown in plate 1, figure 1, and in the sections of text-figures 4 and 5), seems to me to indicate that the posterior and lateral cardinal vessels extend caudalward in connection with chains of angioblasts from the aorta which pass dorsal and ventral to the nephritic tulniles in lines which are very plain in figure 5. In figure 5 of plate 3 is shown a ventral view of the pronephritic vessels in a pig of 20 somites, in w
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Keywords: ., bookauthorcarn, bookpublisherwashingtondc, booksubjectembryology
