OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 155 



being larger in the latter case. In these alveoli also the lumen 

 contains mucin, {c) Finally there are glands in which some 

 alveoli are lined at the same time with granular and mucous cells 

 side by side. 



A similar interesting condition is presented by the mucous 

 glands of the human larynx and trachea, especially of the epi- 

 glottis, where the same alveolus, lined both with granular 

 columnar cells and mucous cells side by side, is the common 

 occurrence. (See also Tarchetti mentioned above.) 



In fig. 5 I have faithfully represented a part of an alveolus of a 

 mucous gland of epiglottis lined by " granular '' cells and mucous 

 cells. It is here also shown that the " granular '' cells possess 

 a striated border, and T have to repeat here what I have 

 stated already several times before, viz. that the strife are due to 

 the fibrils of the cell-substance, and that the bright border- 

 substance is independent of it. If we place side by side the 

 experience thus gained in the examination of the human epi- 

 glottis and oesophagus, we are led to the conclusion that in these 

 organs the state in which mucigen and mucin is present in the 

 gland cells is preceded, or followed respectively, by a state in which 

 the cells possess the same character as for instance the epithelial 

 cells of the intestine, viz. in which the interfibrillar or interstitial 

 substance is present only in an infinitesimal amount, and hence 

 the closeness of the network and the granular appearance. 

 This corresponds very probably to the condition observed by 

 Lavdowsky (1. c.) in the exhausted mucous glands. 



Tlie ducts of the glauds of the Immau oesophagus are in their deeper 

 section lined with a layer of columnar epithelial cells, and oulside this a 

 layer of small polygonal cells ; the former show a beautiful longitudinal 

 striatioii. The same structure is to be observed in tlie columnar epithelial 

 cells lining the ducts of the glands of the human larynx and trachea. 



The occurrence of the columnar 'Agranular" epithelial cells 

 side by side with, and changing into the mucous cells in the 

 glands of the epiglottis of man shows us the identity of this 

 appearance with that observed in the intestine (the surface of the 

 mucosa and in the crypts of Lieberkiihn), viz. the presence of 

 ordinary " granular " columnar epithelial cells side by side with 

 mucous secreting goblet cells and the convertibility of the one 

 into the other. That the mucous cells in mucous glands are 

 identical in shape, structure and function with the goblet cells of 

 the intestine has been mentioned previously more than once. 



Before concluding this chapter I must say a few words con- 

 cerning the " serous "' glands of the tongue treated in so ex- 

 cellent a manner by v. Ebner in his monograph above 

 quoted. The gland cells lining the alveoli of these glands 

 are not composed of " granular " protoplasm as represented by 



