260 



REN. 



very similar to those which may sometimes 

 be seen covering the vessels of the Malpighian 

 tuft. (Vide ante, fig. 160.) 



After the tubes have lost their normal 

 epithelial lining they may undergo one of 

 the three following changes. 1. In some in- 

 stances a peculiar whitish glistening material 

 is thrown into the tubes, some of which 

 escapes with the urine in the form of cylin- 

 drical moulds of the tubes, the appearance of 

 which as seen in the urine is somewhat im- 

 perfectly represented in/g. 173. The effect 



Fig. 173. 



tubes form the serous cysts which are so 

 commonly seen in the cortical portion of the 

 kidney. And it is remarkable that the moni- 

 liforai appearance of the dilated tubes, as seen 

 in the microscopic specimens, is in many 

 instances preserved even when the tube is so 

 much dilated as to form cysts visible to the 

 naked eye. (Fig. 174.) 



Fig. 174. 



Cylindrical moulds of the urinary tubes composed 

 of a peculiar whitish, glistening material, which is 

 sometimes effused into the tubes in the advanced 

 stages of chronic nephritis. From the urine. Mag- 

 nified 200 diameters. 



of this material being effused into the tubes 

 appears to be to obliterate them, and in some 

 instances it apparently becomes organised into 

 fibrous tissue. 



2. Another change which the tubes un- 

 dergo in consequence of losing their epithelial 

 lining, is that of becoming atrophied. The 

 power of separating the solid urinary consti- 

 tuents from the blood resides in the epithelial 

 cells which line the convoluted tubes. After 

 the destruction of the cells the secreting 

 power is lost, and as the normal action of the 

 cells is certainly one of the essential conditions 

 for maintaining the continued flow of blood 

 to the tubes, so the removal of the cells is 

 very commonly followed by a diminished 

 afflux of blood, and a consequent wasting of 

 the tubes. 



3. Another change consequent upon the 

 destruction of the epithelial cells is, in a cer- 

 tain sense, the reverse of the preceding. The 

 tubes appear to retain the power of secreting 

 serum, which fills and dilates the tube in con- 

 sequence of its escape being prevented by 

 epithelial debris choking up the lower ex- 

 tremity of the tube. When once a tube is 

 brought into this condition the process of 

 dilatation may proceed to an almost unlimited 

 extent. The tube bulges in the intervals of 

 the fibrous matrix, and assumes the appear- 

 ance represented in fig. 172 c. These dilated 



Sectiqn of a portion of kidney in which serous 

 cysts have been developed. At a there is a series of 

 four cysts which are probably formed by the dilata- 

 tion of a single tube. Compare this with fo. 172. 

 From a specimen in the museum of King's College. 

 Natural size. 



Mr. Simon, in a paper on " Subacute In- 

 flammation of the Kidney,"* has propounded 

 the theory that these cysts are greatly dilated 

 epithelial germs, which become thus mon- 

 strously developed in consequence of the 

 destruction of the basement membrane of the 

 tubes. 



If Mr. Simon's account of these cysts were 

 correct they would be in fact hydatid cysts. 

 I am not prepared to deny that cysts are ever 

 formed in the kidney by the development of 

 isolated cells, as described by Mr. Simon ; it 

 is very possible that such an occurrence may 

 be not unfrequent, although it has hitherto 

 escaped my observation. But there can, I 

 think, be no doubt in the mind of any one 

 who will carefully examine the subject, that 

 the appearances described and figured by 

 Mr. Simon are produced simply by the 

 packing of the tubes in the fibrous net- 

 work which surrounds and partially conceals 

 them. The best safeguard against a misin- 

 terpretation of appearances in diseased speci- 

 mens is a careful study of the healthy tissues. 

 The peculiar cyst-like appearance of the tubes 

 in cases of chronic nephritis results from the 

 transparency of the tubes when deprived of 

 their epithelial lining. This delicate and 



* Med. Chir. Trans, vol. xxx. 



