OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 169 



liar polyhedral epithelial-like cells that form similar tracts in the 

 matrix of the ovary. Both kinds of cells, viz. those of testis 

 and ovary, are placed by all observers in the same category on 

 account of their similarity of appearance and their development. 

 I notice, however, that in these epithelial-like cells in sections of 

 hardened ovary of kitten, cat and guinea pig, in which animals 

 they occur in considerable quantities, the intracellular network is 

 considerably denser than in the cells of the testis. These cells, 

 — both of the testis and ovary of young and adult animals — are 

 in respect of their morphological characters^ in no way different 

 from epithelial cells, and as regards their development it has been 

 satisfactorily shown that, with reference to the ovary, they are 

 remnants of the epithelium of the Wolffian body (His, Waldeyer, 

 Romiti, and others). Balfour, who describes this same tissue 

 very minutely in the developing ovary of rabbit, dog, cat and 

 sheep,^ as "tubuliferous tissue," also connects it with the Wolffian 

 body. The same holds good also for the interstitial cells of 

 the testis of the adult, viz. they are remnants of the epithe- 

 lium of the Wolffian body that has not been used for the develop- 

 ment of the epithelium of the seminal tubes. Hence, we may 

 justly call them interstitial epithelial cells of the testis and ovary. 



9. The Epithelial Cells of Sebaceous and Sweat Glands. 



[a) The intracellular network of the cells forming the 

 epithelium of sebaceous glands —I only refer to the flask-shaped 

 or tubular secreting parts, not to the ducts — is in many re- 

 spects analogous to that mentioned in the liver cells. If we 

 examine the peripheral parts of a sebaceous gland in sections of 

 skin (of man, but especially of sheep), hardened either in chromic 

 acid, or our mixture of chromic acid and spirit, and stained with 

 logwood, or carmine or picro-carmine, we notice that the sub- 

 stance of the small polyhedral cells lining the membrana 

 propria is not ' granular,^ but consists of a very dense and uniform 

 network, and there is, therefore, hardly any interlibrillar sub- 

 stance perceptible. The cells next these peripheral ones are larger, 

 and the network is more distinct and open, and the nearer to 

 the centre of the tube the larger are the cells, and the more open 

 is the network (see fig. 16). The interfibrillar substance which is 

 here the fatty matter constituting the sebum, increases therefore 

 as the cells approach the centre, and thus the network becomes 

 more open.^ This network is visible only after the removal of 



1 Neither KoUiker (' Gewebelehre,' iS67, p. 524), nor Henle (Splancli- 

 uologie,' p. 358), gives a correct description of these cells. 



" L. c, p. 422. 



3 The reticular nature of the substance of these cells has been demonstrated 

 to me by my friend Mr. McCarthy several years ago. 



