324 DIGESTION OF PROTEIDS. [BOOK n. 



in the same way, a similar solution takes place. The readiness 

 with which the solution is effected, will depend, cceteris paribus, 

 on the smallness of the pieces, or rather on the amount of surface 

 as compared with bulk, which is presented to the action of the 

 juice. 



Gastric juice then readily dissolves coagulated proteids, which 

 otherwise are insoluble, or soluble only, and that with difficulty, 

 in very strong acids. 



When proteids, which are soluble in water or in dilute acid, 

 are treated with gastric juice, no visible change takes place; but 

 nevertheless, it is found on examination that the solutions have 

 undergone a remarkable change, the nature of which is easily seen 

 by contrasting it with the change effected by dilute acid alone. 

 If raw white of egg, largely diluted with water and strained, be 

 treated with a sufficient quantity of dilute hydrochloric acid, the 

 opalescence or turbidity which appeared in the white of egg on 

 dilution (and which is due to the precipitation of various forms 

 of globulin accompanying the egg-albumin in the raw white) dis- 

 appears, and a clear mixture results. If a portion of the mixture 

 be at once boiled, a large deposit of coagulated albumin occurs. 

 If, however, the mixture be exposed to 50 or 55 C. for some 

 time, the amount of coagulation which is produced by boiling a 

 specimen becomes less, and, finally, boiling produces no coagula- 

 tion whatever. By neutralisation, however, the whole of the 

 albumin (with such restrictions as the presence of certain neutral 

 salts may cause) may be obtained in the form of acid-albumin, 

 the filtrate after neutralisation containing no proteids at all (or a 

 very small quantity). Thus the whole of the albumin present in 

 the white of egg may be, in time, converted, by the simple action 

 of dilute hydrochloric acid, into acid-albumin. Serum-albumin 

 similarly treated undergoes, in course of time, a similar conversion 

 into acid-albumin, and we have already seen ( 56) that solutions 

 of myosin or of any of the globulins are with remarkable rapidity 

 converted into acid-albumin. Thus simple dilute hydrochloric of 

 the same degree of acidity as gastric juice, merely converts these 

 proteids into acid-albumin, the rapidity of the change differing 

 with the different proteids, being in some cases very slow, and 

 requiring a relatively high temperature. 



If the same white of egg or serum-albumin be treated with 

 gastric juice instead of simple dilute hydrochloric acid, the events 

 for some time seem the same. Thus after a while boiling causes 

 no coagulation, while neutralisation gives a considerable precipitate 

 of a proteid body, which, being insoluble in water and in sodium 

 chloride solutions, and soluble in dilute alkali and acids, at least 

 closely resembles acid-albumin.. But it is found that only a 

 portion of the proteid originally present in the white of egg or 

 serum-albumin can thus be regained by precipitation. Though 

 the neutralisation be carried out with the greatest care it will be 





