i^ PROCEEDINGS OF THE CANADIAN INSTITUTE. 



pancreatic cells of the dog, and he suggests the name of "pre-zymogen" for the 

 substance. Some information as to the nature of this substance is afforded by the 

 researches of Dr. Macallum, who describes '3 the differences in staining exhibited by 

 the nucleus and plasma of the exhausted and resting pancreatic cell, and explains this 

 difference as follows; — "The chromatin of the nucleus of the pancreatic cell gives rise 

 to a substance which we may call "prozymogen," sometimes dissolved in the nuclear 

 substance, sometimes collected in masses (plasmosomata), and finally diffused into 

 the cell protoplasm, uniting with a constituent of the latter as zymogen." In a 

 subsequent investigation'" into the distribution of assimilated iron compounds in 

 animals and vegetable cells. Dr. Macallum found diffused in the cytoplasm of the 

 outer zone of the chief cells, and, with two exceptions, in the cytoplasm of all other 

 glands examined by him, a firm compound of iron, and his observations led him 

 to conclude that this iron compound was the prozymogen of his earlier researches. 

 It seemed probable that the fibrillar chromophilous element observed by me in the 

 outer zone of the chief cell was the prozymogen of Dr. Macallum's investigation; 

 and this proved to be the case. A convenient means of proving this was afforded 

 by the fact that the chief ceils of the greater curvature of the rabbit's stomach 

 contain at all periods of digestion a very large amount of the chromophile substance, 

 which in the exhausted phase almost fills the entire cell, the zymogen granules being 

 then confined to a narrow band next to the lumen. Sections of this mucous 

 membrane give no immediate reaction for iron with ammonium sulphide, but after 

 three hours' treatment with a three per cent, solution of sulphuric acid in alcohol, at 

 a temperature of 40 degrees C, those portions of the chief cells containing the 

 chromophile substance take, with acid ferrocyanide solution, a deep Prussian blue 

 color, which is so intense as almost to mask the nucleus of the cell. The 

 Prussian blue reaction also shows the same fibrillar structure as is observed in 

 sections stained in haematoxylin. We may, therefore, use the term " prozymogen "" 

 for this substance wherever it occurs. 



It is not in the chief cells of the stomach and in the pancreatic cells alone that 

 the prozymogen assumes the fibrillar form. I have observed similar structures in 

 the serous glands of the gustatory area of the rabbit and dog, and it is possible 

 that the rod-like structures described by Solger's jn the basal portion of the cells 

 of the human submaxillary gland, and by Erik Mueller'* in the cells of the 

 submaxillary of the guinea pig, may belong to the same category. The fibrillation 

 in the prozymogen of the gastric gland cells may be observed in the fresh cell, 

 examined in aqueous humour, and is, therefore, not the product of the action o'f 

 reagents. It may be also seen in sections fixed in Hermann's or Vom Rath's 

 osmic acid mixtures, and in aqueous sublimate. 



The cells of the neck of the gland are quite different in appearance from those 

 of the body. At no period of digestion do they contain either prozymogen or 

 granules of zymogen. The same remark is applicable to the chief cells of the short 

 collecting duct (sammelgang of Bizzozero), and to the cells of the lower portion 

 of the mouth of the gland. The cells of these three regions have many features in 

 common, and will be described together. As a starting point, I will describe the 

 cells of the upper portion of the neck of the gland. 



These cells are usually conical or pyramidal in shape, wedged in between the 

 larger oval border cells of this region of the gland in such a way that the broad 

 base of the cell is directed towards the lumen. In vertical sections of the mucous 

 membrane, from one to four of these cells may usually be observed between each 

 pair of the border cells. Two zones may be distinguished in the cells, an outer 

 •protoplasmic zone of fine reticular structure, staining readily with eosin, and an 



(13) Op. Cit. 



(14) Quarterly Journal Microscopical Science. Vol. XXXVIII., Part II. New Ser. 



(15) Anatomischer Anzeiger. Bd. IX, 



(16) Archiv f. Mik. Anat. Bd. XLV. 



