. The biology of the frog . nd of a fingerof a glove. The capsule, however,has grown around the glomerulus andclosely surrounds the afferent and effe-rent vessels. At the dorsal side of thecapsule, and usually opposite the pointwhere the blood vessels enter, the outerwall passes into the neck of the urinif-erous tubule. The very thin cells ofthis wall shade off gradually into cellsof columnar epithelium which for ashort distance carry very large the neck, which is somewhatnarrower than the rest of the tubule, the cells are lined withmuch shorter cilia. Each tubule is lined with a
. The biology of the frog . nd of a fingerof a glove. The capsule, however,has grown around the glomerulus andclosely surrounds the afferent and effe-rent vessels. At the dorsal side of thecapsule, and usually opposite the pointwhere the blood vessels enter, the outerwall passes into the neck of the urinif-erous tubule. The very thin cells ofthis wall shade off gradually into cellsof columnar epithelium which for ashort distance carry very large the neck, which is somewhatnarrower than the rest of the tubule, the cells are lined withmuch shorter cilia. Each tubule is lined with a single layerof cells which varies in character in the different course of each tubule is quite complicated. At first itruns dorsally, where it forms a more or less complicated coil,then it proceeds to the ventral side of the kidney, forms asecond coil, and finally runs dorsally again, emptying intoone of the collecting canals which extend transversely acrossthe dorsal surface of the kidney from the inner margin to. Fig. 53. —A urinifer-ous tubule, c, col-lecting tubule, m,Malpighian body;t, uriniferous tubuleleading from the lat-ter to the collectingtubule. (After Nuss-baum.) 204 THE BIOLOGY OF THE FROG CHAP. the ureter. The tubules are held together by connectivetissue which forms a support also for the numerous blood vessels with which the kid-ney is supplied. The ventral surface ofthe kidney is furnishedwith numerous ciliatedfunnels, the nephrostomes,whose expanded ends openinto the ccelom. At theirother end the nephrostomesempty into branches of therenal veins, and the ciliawith which they are linedbeat toward the upper endof these organs and thuscreate a current of lymphfrom the body cavity intothe blood. This relationof the nephrostomes is apeculiar one and occursonly in the Anura. Thelower Amphibia preservethe typical arrangement ofthese organs, as the nephro-stomes are connected with the renal tubules. This condi-tion, as Marshall has found, occurs also in t
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