CHYMIFICATION. 553 



order in which each separate article of food is mentioned above, indicates 

 its relative digestibility, at least in the stomach of Alexis St. Martin. 



As a rule, animal substances are more rapidly digested than vege- 

 table substances. The rate of digestion of different substances corre- 

 sponds with the relative necessity for their being acted on by the gas- 

 tric juice. Thus, those which require the most digestion by that fluid, 

 necessarily remain the longest, whilst those which are merely liberated, 

 but are not dissolved in it, pass out sooner; and fluids, with their soluble 

 ingredients, disappear the most quickly. In cases of fistulous openings 

 in the dog, and in Man, it has been found that fibrin is digested in 

 half an hour, casein in 1J hour, gelatin in 2 hours, coagulated albumen 

 in 6 hours, and tendons in 10 hours. 



During gastric digestion, the muscular tissue breaks up first into its 

 fasciculi, and then into fibres, the striae of which gradually disappear, 

 the sarcolemma, as well as its sarcous contents, being dissolved ; frag- 

 ments of the fibres, however, pass into the intestine, and there under- 

 go further, though, it may be, incomplete, digestion. Yellow elastic 

 tissue appears to resist the action of the gastric juice; tendinous fibres 

 dissolve slowly ; white areolar fibres are totally dissolved. The cor- 

 puscles of cartilage are not digested, but the intercellular substance 

 undergoes solution. The areolar fibres of adipose tissue disappear, 

 and frequently also the walls of the fat-cells; but their fatty contents 

 are commonly said to resist the action of the gastric juice; fat, how- 

 ever, may begin to be broken up into the fatty acids. (Marcet.) Of 

 vegetable tissues, the cellulose or lignin of the cell-walls, including the 

 dotted, annular, and spiral ducts, for the most part resist the action 

 of the gastric fluid, which is also inoperative upon starch grains, though 

 it does not interfere with, or totally arrest the action of the swallowed 

 saliva, and of the mucus of the stomach upon starch. Chlorophyll, the 

 green coloring matter of plants, appears to resist digestion ; but the 

 pectinous and albuminoid contents of vegetable cells, are completely 

 dissolved. 



Chymification and Chyme. 



The general product of digestion in the stomach, resulting from the 

 combined admixture with the food, and the action upon it, of the saliva, 

 the mucus of the mouth and stomach, and the gastric juice itself, is 

 called the chyme; the process of its formation is named chymification. 

 The chyme is a thick, pulpy, grumous fluid, containing the food thus 

 far digested, together with partially digested and indigestible matters ; 

 it has a strong sour smell and taste, and an acid reaction. The degree 

 of acidity of the chyme varies, however, according to the quantity of 

 acid, such as lactic or acetic acid, in the food, and also according to 

 the relative quantities of saliva and gastric juice contained in it, much 

 gastric juice rendering it more acid, and an excess of saliva less so. 

 The color of the chyme depends on the food, being whitish in an infant 

 fed on milk and farinaceous food, but of a brownish hue when meat is 

 eaten, or greenish after vegetable diet ; sometimes, also, it is tinged 

 with bile, which has ascended into the stomach. The presence of saliva, 

 mucus, and gastric juice, is indicated by characteristic microscopic nu- 



