170 DR. £. KLEIN. 



the fatty interfibrillar substance, on account of the high refrac- 

 tive index of this latter. (In preparations mounted in dammar 

 varnish or Canada balsam solution, this is effected by passing the 

 sections first through alcohol and then through oil of cloves.) 



All these cells possess a nucleus containing a uniform network . 



Towards the duct the nucleus of the cells becomes indistinct 

 and the intracellular network is reduced to a few membranous 

 streaks, between which the fatty matter is enclosed. Thus the 

 epithelial cells lining the alveoli of sebaceous glands are in all 

 respects analogous to the other secreting cells, especially mucus- 

 secreting cells; in mucus-secreting cells we had mucin as 

 the result of the change of the interfibrillar substance; 

 in the epithelial cells of sebaceous glands we find it to 

 be a fatty substance. In many secreting glands we found a 

 contrast between the cells in the state of secretion and such as are 

 not secreting, the former showing the intracellular network open, 

 owing to the greater amount of interfibrillar substance under- 

 going the metabolic change, the latter possessing a more 

 " granular" aspect, i. e. the network being much closer. And 

 the same relation we find to obtain also in the sebaceous glands ; 

 for the peripheral cells with a dense intracellular network 

 C granular " protoplasm) bear to the more centrally situated 

 cells — those containing an open network and a fatty interfibrillar 

 substance — evidently the relation of a non-secreting to secreting 

 cells of other glands. 



The epithelial cells lining the alveoli of the Meibomian glands 

 of the eye-lids are in every respect analogous to those of the 

 ordinary sebaceous glands ; it is, therefore unnecessary for me to 

 enter into details, as I should have only to repeat what I 

 stated just now with regard to the latter glands. 



In the embryo at an early stage the alveoli of both ordinary 

 sebaceous and Meibomian glands contain only " granular " cells, 

 i. e. cells in which no fatty matter is yet contained in the intracel- 

 lular network, hence the great closeness of this latter. 



The question might be asked, whether in the process of 

 secretion the substance secreted is directly derived from the intra- 

 cellular network or only indirectly so, i. e. from the interstitial 

 substance contained in its meshes ? 



From what I have repeatedly stated on the occasion of the 

 submaxillary, the mucous and sebaceous glands, the reader will, 

 I think, have come to the conclusion that it is the interfibrillar 

 substance which becomes increased in amount and converted into 

 the matter that is to be secreted, and not the intracellular net- 

 work itself. This latter is not used up, therefore, during secretion, 

 in the sense in which, for instance, Heidenhain and Lavdowsky 

 assumed it to be, but only alters its arrangement in such a 



