CHAP. XXXIV.] VESSELS UNCOVERED BY EPITHELIUM, 



489 



tinues in very active motion many hours after the death of the 

 animal (vide Fig. 3, Vol. I.) In the newt, and in some snakes and 

 other reptiles, the tube is completely lined with ciliated epithelium 

 throughout ; and by the activity of the motion, the epithelium can 

 be traced for one-third of the way within the capsule. Ciliated 

 epithelium has not yet been demonstrated in the kidneys of mam- 

 malia; but in one instance Gerlach has seen it in the kidney of 

 the fowl. In various fishes and in many reptiles it is very fre- 

 quently met with. 



The statement of Gerlach and other observers, that the vessels 

 of the Malpighian tuft are invested with epithelium, may be ex- 

 plained by the fact, that small granular or nucleated cells may be 

 frequently observed in connexion with the vessels. After repeated 

 and careful observation, we are convinced that these cells are situ- 

 ated either within the vessel itself or enclosed in its wall (Fig. 233). 

 In the tuft of batrachian reptiles, the fig. 233. 



white corpuscles of the blood often 

 give the idea of being connected 

 with the wall of the vessels, instead 

 of lying in their interior. When 

 the vessels are much shrunken, and 

 their walls a little plaited, or corru- 

 gated, the appearance of cells lying 

 upon the little capillary loops is pro- Small portion of a loop of ca])illarv vessels 

 rhioed when thrso loons ire seen in of ne tuft of the kldney " f the large water 



1 newt (Triton cristntus), showing nnc : ei 



Tirnfilp WphnwliPPn nhlp in minv within the wall of the vessel. The line above 

 lie< t aOie, II naoy the vessel is the outline of part of the capsule. 



instances, however, to demonstrate Ma * niflcd 215 ^erer*. 

 small oval or circular cells within the wall of the capillary vessel 

 itself, and are inclined to look upon these as the nuclei of 

 vessels. Here and there a granular cell may sometimes be detected 

 on the surface, but they are very few in number and irregular in 

 their arrangement ; and we are satisfied that it cannot be regarded 

 as a fact of any physiological importance, and that the vessels of 

 the tuft are really bare within the capsule. 



Convoluted Portion of the Tube. From the capsule of the Mal- 

 pighian tuft, we pass to the convoluted portion of the tube, which 

 is directly continuous with it. This is composed of a delicate base- 

 ment membrane, lined by epithelium. Externally, the basement 

 membrane is in close contact and probably incorporated with the 

 matrix of the organ; and it is in immediate relation with an abund- 

 ant capillary plexus, which carries the blood after it has passed 

 through the vessels of the Malpighian body. It is from this blood, 



VOL. II. K K 



