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in common, due to the presence in them of the substances antecedent 

 to the secretion. Lang ley, long ago showed that in the serous salivary 

 glands and in the chief cells of the gastric glands, the antecedent to 

 the ferment was stored up in the form of granules of zymogen in the 

 distal segment of the cell. These granules have been shown by 

 Macallum in the pancreas to contain phosphorus in an organic com- 

 bination which can be demonstrated by Macallum's modification of the 

 Libenfeld and Monti microchemical reaction for organic phosphorus. 

 Furthermore it has been shown by various authors — first of all by 

 Solger ('94) — that these zymogenic serous cells contain uniformly 

 in their basal cytoplasm an intensely chromophile substance, frequently 

 giving the appearance of parallel filaments — the basal filaments. 

 The substance of these basal filaments I have shown, in the gastric 

 chief cells, to contain iron in a masked organic combination, which 

 can be demonstrated by the use of Macallum's microchemical reaction 

 for iron. I have, moreover, shown that this substance diminished and 

 increases, pari passu, with the increase and diminution of the 

 zymogen granules of which it is probably the andecedent substance. 

 I have therefore used the name, prozymogen, for this substance. For 

 the same substance, the French writers, Cade ('01) and Garnier ('00) 

 have used the term ergastoplasma. 



The presence of these two substances, zymogen and prozymogen, 

 in the zymogenic serous cell enables us to substitute for staining 

 reactions whith are merely empirical tests, the positive and conclusive 

 microchemical tests for the elementary constituents iron and phosphorus. 



The mucous cell, it is true, stores up its reserve secretion in the 

 form of granules, but these granules are so similar in refractive 

 index to water that they are with difficulty visible in the fresh cell. 

 Moreover, when they are tested microchemically, for phosphorus, the 

 result is absolutely negative. The mucous cell does not contain basal 

 filaments and the microchemical test for iron gives a relatively feeble 

 reaction in the basal cytoplasm. In these respects the cells of the 

 glands of Brunner with the exception of the dark cells of the glands 

 of Brunner of the rabbit, react precisely like mucous cells from the 

 salivary glands, they do not contain basal filaments, the basal cyto- 

 plasm gives a comparatively feeble reaction for iron, and the accumu- 

 lated secretion gives negative results when tested microchemically for 

 organic phosphorus. 



Thus all the evidence, positive evidence as to the structure and 

 staining reaction of the cells, negative evidence, as to the absence 

 from them of the characteristic substances present in zymogenic cells, 



