DIGESTION IN THE STOMACH 771 



is really a division of the complex molecule into smaller molecules, 

 which are qualitatively different. Thus of the fractions which he 

 obtained, some contain the greater part of the sulphur originally 

 present in the protein molecule, another contains the greater part 

 of the carbohydrate group, while others are free altogether from 

 the tryptophane group which is responsible for Hopkins' reaction 

 obtainable in the original protein. 



Proceeding from primary through secondary albumoses to peptones, 

 there is probably a continuous diminution in the size of the molecule. 

 During the time which gastric juice has to exert its influence, a 

 maximum, say, of twelve hours, the breakdown of proteins never 

 passes beyond the albumose and peptone stage, and it is in this 

 form that the proteins of the food pass on through the pyloric orifice 

 into the small intestine. 



ACTION ON THE CONNECTIVE TISSUES AND OTHER 

 FOOD-STUFFS ALLIED TO PROTEINS 



COLLAGEN. The connective tissues are made up chiefly of white 

 fibres, more or less modified, which consist of collagen. This substance 

 forms the main basis of areolar tissue, of white fibrous tissue, and of 

 bone. On prolonged boiling, it is converted into gelatin. The gastric 

 juice dissolves collagen, converting it, probably through the stage 

 of gelatin, into gelatoses and gelatin peptones, bearing the same 

 relation to the original substance as is borne by the proteoses and 

 peptones to the proteins. On account of this action, adipose tissue 

 (which consists of protoplasmic cells distended with fat, and bound 

 together by connective tissue) is broken up into its constituent 

 cells. The protoplasmic pellicle is dissolved, and the fat floats freely 

 in the gastric juice. 



ELASTIN, which also occurs in varying amounts as the chief 

 constituent of the elastic fibres of connective tissues, is slowly acted 

 upon by gastric juice. Under the conditions of natural digestion, 

 however, it may be regarded as indigestible. 



MUCIN, which forms a considerable proportion of the ground 

 substance of connective tissues, is converted by gastric juice into 

 peptone-like substances, and into reducing bodies probably allied 

 to glycosamine. 



The NUCLEO-PROTEINS, the chief constituents of cells, and therefore 

 ingested in large amounts with food-stuffs such as sweetbreads, are 

 first dissolved by the acid of the gastric juice, and are then broken 

 up into two moieties. The protein half is converted into proteoses 

 and peptones, while the nuclein moiety is precipitated in an insoluble 

 form, 



