CHANGES IN THE GLANDS DURING SECRETION. 327 



digestion, the chief cells become enlarged and moderately turbid or 

 granular, the parietal cells also enlarge, while the pyloric cells remain 

 unchanged. The chief cells become diminished and more turbid or 

 granular until the 9th hour, the parietal cells are still swollen, and 

 the pyloric cells enlarge. During the last hours of digestion, the chief 

 cells again become larger and clearer, the parietal cells diminish, the 

 pyloric cells decrease in size and become turbid (Figs. 137 and 138). 



[Langley gives a different description of the appearances presented by these cells, 

 during different phases of secretory activity. The results may be reconciled by 

 remembering that the gland-cells were examined under different conditions. The 

 secretory cells consist of a cell-substance composed of (a) a framework of living 

 protoplasm, either in the form of an intra- cellular fibrillar net-work (Klein), or in 

 flattened bands. The meshes of this framework enclose at least two chemical 

 substances, viz., (b) a hyaline substance in contact with the framework, and 

 (c) spherical granules which are embedded in the hyaline substance (Langley). 

 Speaking generally, during active secretion, the granules decrease in number and 

 size, the hyaline substance increases in amount, the net-work grows. This is the 

 reverse of what is stated above as the observation of Heidenhain, but the granular 

 appearance described by Heidenhain after secretion is very probably due to the 

 action of the hardening agent, alcohol. Langley found that in the living con- 

 dition, or after the use of osmic acid, in some animals at least, the chief cells are 

 granular during rest, but during a state of activity two zones are differentiated, 

 an outer one, which is clear, owing to the disappearance of the granules, and an inner 

 more or less granular one. Granules reappear in the outer part after rest. Dur- 

 ing digestion, the parietal cells increase in size, but do not .become granular. In 

 all cells containing much pepsinogen, distinct granules are present, and the quan- 

 tity of pepsinogen varies directly with the number and size of the granules. In 

 the glands of some animals there is little difference between the resting and active 

 phases (Langley). Compare Serous Glands, p. 284, and Pancreas, 168.] 



The Pepsin is formed in the chief cells (Heidenhain). When these 

 are clear and large they contain much pepsin, when they are contracted 

 and turbid the amount is small (Griitzner). The pyloric glands are 

 also said to secrete pepsin, but only to a small extent (Ebstein, Griitzner, 

 Klemensiewicz). Pepsin accumulates during the first stage of hunger, 

 and it is eliminated during digestion and also during prolonged hunger. 

 According to Ebstein, Griitzner, and Langley, pepsin as such, is not 

 present within the cells, but only a " mother-substance," a pepsinogen 

 substance (zymogeri), which occurs in the granules of the chief cells 

 (Langley). This zymogen or mother-substance by itself, has no effect 

 upon proteids; but if it be treated with hydrochloric acid or sodium 

 chloride, it is changed into pepsin. Pepsin and pepsinogen may be ex- 

 tracted from the gastric mucous membrane by means of water free from 

 acids. 



The pyloric glands secrete pepsin, but no acid. Klemensiewicz excised in a living 

 dog the pyloric portion of the stomach, and afterwards stitched together the 

 duodenum and the remaining part of the stomach. The excised pyloric part with 

 its vessels intact, he stitched to the abdominal wall, after sewing its lower end. 



