20 



Mr. J. N. Langley. On the Histology and [Mar. 24, 



indicate) may differ in different animals according to their habits and 

 modes of activity. 



The resnlts we have obtained are capable of numerous physiological 

 and pathological applications, but for the present we content ourselves 

 with the above brief statement of some of the more obvious conclu- 

 sions which they seem to justify. 



III. " On the Histology and Physiology of the Pepsin -forming 

 Glands." By J. N. Langley,. M.A., Fellow of Trinity 

 College, Cambridge. Communicated by Dr. Michael 

 Foster, F.R.S. Received March 11, 1881. 



(Abstract.) 



This paper contains an account of observations upon Bana temporaria, 

 Bufo vulgaris, Triton twniatus, Triton oristatus, and Coluber natrix. 



In these animals the changes which take place in the pepsin-forming 

 glands under various conditions, viz., digestion of varying amounts of 

 food, attempted digestion of indigestible substances, as sponge, and 

 fasting, were noted. 



Omitting the pyloric glands, which in these animals form only a 

 minimal amount of pepsin, all the pepsin-forming glands present 

 certain phenomena in common. In all, the living gland- cells contain 

 granules, which diminish during digestion. In each the amount of 

 pepsin* contained by a definite weight of the gland-bearing mucous 

 membrane is proportionate to the amount of granules contained by the 

 gland-cells. An increase or diminution of the cell-granules, in what- 

 ever way it is brought about, is accompanied by a corresponding 

 increase or diminution in the pepsin-content of the cells. Further, in 

 different parts of the pepsin-forming region the amount of pepsin 

 present is proportional to the granularity of the cells. 



Hence we may conclude that the granules consist wholly, or in part, 

 of pepsin or of some substance capable of giving rise to pepsin. 



In some of these animals certainly, and probably in all, the fresh 

 glands contain only a minimal quantity of pepsin, but, on the other 

 hand, a large quantity of a substance from which pepsin can be 

 obtained, i.e., zymogen. It follows, then, that in the previously men- 

 tioned estimation of pepsin, the pepsin found resulted from the splitting 

 up of zymogen, and consequently that the amount of zymogen con- 

 tained by the gland-cells is proportional to their granularity. 



* The dried mucous membrane was extracted with one hundred times its weight 

 of hydrochloric acid, 0*2 per cent. G-riitzner's colorimetric method was used in 

 making the estimations. 



