136 DR. E. KLEIN. 



8. The epithelial cells lining the seminal tubules, and the 

 interstitial epithelium of testis and ovary. 



9. Epithelial cells of sebaceous glands and of sweat-gland 

 tubes. 



1. The EpitJielium of the Intestine. 



(«) Of the villi of the small intestine. — The first impression 

 that one obtains by examining with a good lens in a thin section 

 of well-hardened and well-stained intestine of a mammal, such 

 as man, dog, cat, rabbit, &c., is that the substance of the epi- 

 thelial cells covering the villi is composed not simply of '^ granu- 

 lar " protoplasm, but that it is, in addition, longitudinally striated. 

 By examining the cells more attentively it is seen that this longi- 

 tudinal striation is the expression of fibrils running parallel with 

 the long axis of the cells. These fibrils extend all through the 

 cell-substance from the basis to the free edge. Such is the 

 appearance presented by the epithelium when examined with a 

 good lens — e.g. Zeiss' E or E, or HartnacFs immersion No 10 — 

 fresh in aqueous humour or after maceration in iodized serum. 

 The best view, however, of this condition I have had in the epi- 

 thelium covering the villi of pig's intestine. The intestine had 

 been hardened in a mixture of two parts of 4- per cent, chromic 

 acid and one part of methylated spirit. In a portion of a section 

 well stained with hfematoxylin, which presents the epithelium 

 only in a very thin layer, we notice from place to place, on and 

 between the fibrils, fine '^ granules," which on careful focussing, 

 are distinctly recognised as the optical sections of fibrils ; these 

 are identical with horizontal fibrils that unite the longitudinal 

 ones into a network. Thus, the substance of the cells is com- 

 posed of a network of fibrils — intmcelhdar network — of which 

 the greater number have a prevalently longitudinal arrange- 

 ment (see fig. 1, Plate YII). Preparations of intestine hardened 

 simply in spirit, show the epithelial cells more "granular" than 

 the above fluids, but still it is possible to recognise, even with a 

 moderately high power, that the substance of the cells is longitu- 

 dinally striated. And examining the cells with a high power and 

 under good light, it is possible to convince ourselves of the fact 

 that the " granules " can be " focussed " into fibrils, i. e. are 

 the expressions of fibrils viewed in optical sections. However 

 dogmatic the foregoing description may appear, I can only say 

 that I have merely described facts which appear to me perfectly 

 clear if I examine any well prepared thin section of small intestine 

 with a good high power, such as Zeiss ' E or Hartnack's immer- 

 sion 10, and with strong light, 



I may mention here that I obtained also good results by preparing small 

 pieces of intestine of the above animals, according to the method described 



