THE UllINARY ORGANS. 



599 



coat, which in its chemical characters is very closely allied to the sarco- 

 Icmma [vid. § 58), lies a single layer of polygonal, moderately thick 

 cells, surrounding the cavity of the tubuhis, which, from the readiness 

 Avith which they alter, have given rise to many erroneous representations 

 respecting the structure of the urinary ducts and their contents. For 

 instance, in the usual mode of examination in water, they expand, 

 owing to its absorption and become vesicularly distended, so that their 

 polygonal form and regular arrangement are lost ; the renal ducts, 

 within the structureless membrane, appearing to be entirely filled Avith 





rounded larger cells and no longer to possess any cavity. The cells, 

 also, frequently burst, in which case the tuhidl contain nothing but a 

 fine granular substance, with 7i2tclei and clear albuminous drops escaped 

 from the cells. In kidneys not quite fresh, these changes proceed 

 spontaneously ; and, therefore, it is, above all things, necessary to exa- 

 mine the organ as soon as possible after death and to avoid all additions 

 capable of producing change. The contents of the epithelium cells 

 are, besides round nuclei of the usual kind, a most usually, very finely- 

 granular substance, which, on the addition of water, affords clear, light- 

 yellowish drops, probably of albumen, but is not otherwise changed ; 



Fig. 246. — Two straight tuljuli uriniferi of Man, one with perfect epithelium, the other 

 half empty: a, membmna propria ; b, epithelium. 



Fig. 247. — 1, a Majpighian corpuscle, ^, with the tubuhis urini/erus springing from it, 

 B, C ; Human; magnified 300 diam.; figure half-diagrammatic: a, membrane of the Mal- 

 pighian boily, continuous at b, with the mcmbrana propria of the convoluted tubule; c, epi- 

 thelium of tlieMalpighian body; rf, that of the tubule; f, dftaehed epithelium ;/, i'a« affercns ; 

 g, vas efftrens; h, glomerulus Malpighianus. 2, three ci)ithelial cells from the convoluted 

 tubule, magnified 350 diam.; one with oil drops. 



