REN. 



253 



covering the surface of the basement mem- 

 brane. They are granular and opaque, and 

 appear to contain a considerable quantity of 

 solid matter. The cell wall is very delicate, 

 and when water is added to the specimen, the 

 cells frequently fall in pieces very rapidly. In 

 this respect the cells of the kidney differ re- 

 markably from the hepatic cells, the latter 

 having a much thicker and firmer wall, which 

 offers a greater resistance to the action of 

 water. The cells have a distinct nucleus, and 

 in the centre of this in many instances 

 a nucleolus is clearly visible. (Fig. 



Fig. 164. 



a, b, c, d, epithelial cells from a healthy kidney. 

 a contains no oil ; b, c, d, contain a few small oil 

 globules in their interior, e, f, g, h, epithelial cells 

 from a kidney affected with fatty degeneration ; the 

 oil globules are much larger and more numerous 

 than in the cells from the healthy kidney, m, por- 

 tion of a urinary tube from a kidney affected with 

 fatty degeneration, k, I, fibrinous moulds of the 

 urinary tubes from the urine of a patient with 

 fatty degeneration of the kidney, each cylindrical 

 mould entangles blood corpuscles, and a cell having 

 a considerable number of oil globules in the interior. 

 Medic. Chir. Trans, vol. xxix. Magnified 400 dia- 

 meters. 



Another interesting feature in the renal se- 

 creting cells consists in their containing in 

 some cases minute particles of oil. In a 

 perfectly healthy kidney, the quantity of oil 

 contained in the epithelium is very small ; 

 sometimes, indeed, it is difficult to find any 

 cells which contain even the most minute 

 particles of oil, while in other instances, where 

 there is every reason to consider the organ 

 quite healthy, the quantity of oil is much more 

 considerable. When this material accumu- 

 lates beyond a certain extent which it is diffi- 

 cult to define, it must be considered as morbid, 

 and a great excess of oil in the secreting cells 

 constitutes a main feature of one of the most 

 serious and intractable diseases to which the 

 kidney is liable. 



The epithelium lining the straight tubes of 

 the pyramids differs essentially from that of the 



convoluted tubes ; the latter, as before stated, 

 is the true spheroidal or glandular variety of 

 epithelium ; while the former approaches more 

 nearly to the lamelliform or scaly variety. 

 Its particles are smaller and more flattened, 

 so that the epithelium in the medullary cones 

 constitutes a much smaller proportion of the 

 thickness of the tubes than does that in the 

 convoluted tubes of the cortex. (Fig. 163.6.) 

 The canal of the tubes in the medullary cones 

 is also greater in proportion to the thickness 

 of the wall than in the convoluted tubes. 

 The cells in this portion of the tubes have 

 uniform, smooth, and transparent walls, and 

 their interior is less opaque and granular than 

 is the case with the glandular cells before 

 described. Another distinctive character con- 

 sists in the fact of these cells seldom, if ever, 

 containing oil. 



Ciliary motion in the tubes. The preceding 

 description of the epithelial lining of the 

 uriniferous tubes corresponds in most par- 

 ticulars with the usually received account of 

 these structures. There now remain to be 

 stated certain facts which probably are not 

 generally known even to those who are ac- 

 customed to make microscopical examinations 

 of the kidney. In 1845, A. Kolliker published 

 a short paper *, in which he mentions the 

 interesting fact, that in the kidney of the em- 

 bryo lizard the uriniferous tubes are lined by 

 an epithelium remarkable for distinctly deve- 

 loped ciliary processes, which may be seen in 

 vigorous action for some time after the death 

 of the animal. The ciliated epithelium, 

 according to Kolliker's observation, exists 

 throughout the whole length of the tubes, 

 except at the extremities next the common 

 excretory duct. He also observed the cilia 

 at the entrance of the Malpighian capsule. 

 In a note appended to the same paper, the 

 editor (J. Miiller) states that he has observed 

 the same phenomenon in the uriniferous tubes 

 of a fish (Raia clavata). The cilia are very 

 large and long ; they are directed along the axis 

 of the tube, and have a wavy motion like that 

 of a whip-lash. 



In the spring of the present year, before 

 I was aware of the observations just now 

 referred to, while examining the kidney of 

 the newt (Triton and Lissotriton), I was 

 surprised to find vibratile cilia in active mo- 

 tion, not only within the Malpighian cap- 

 sule as described by Mr. Bowman in the frog, 

 but apparently extending throughout the 

 whole length of the uriniferous tubes. I have 

 since looked for this wonderful phenomenon 

 in many of the animals just now mentioned, 

 and have never failed to detect it in any one 

 of the kidneys examined. The part of the 

 kidney most favourable for the examination of 

 this ciliary motion is the anterior extremity, 

 where it is very thin and transparent, so that 

 after being cut away with sharp scissors it 

 requires no further preparation for micro- 



* Ueber Flimmerbewegungen in den Primordial- 

 Nieren. Miiller's Archiv. 1845, and Edinburgh 

 Med. and Surg. Journal, vol. Ixviii. 



