iv DIGESTION IN THE INTESTINE 211 



juice is that with the latter boiled egg-white and other solid foods 

 are softened and split up without previous swelling, and that only 

 the muscular fibrils of meat are digested, while the connective 

 tissue and the collagenic tissues in general are left undigested 

 (Ludwig and Ogata). 



The proteolytic activity of the pancreatic juice has been 

 estimated by different methods with results that are not always 

 comparable ; and there are conflicting opinions as to the laws by 

 which the digestive power of the pancreatic juice is developed. 

 According to Mett's method, trypsin digestion follows the law of 

 Schiitz and Borissow ; according to Gross, on the contrary, it is 

 in direct ratio with the concentration of the ferment. 



Method of Gross (1907). One or two drops of the fluid to be examined 

 (or more if required) are placed in test-tubes containing 10-20 c.c. of a O'l per 

 cent solution of caseinogen and sodium carbonate. This is placed in the 

 thermostat, and samples taken at intervals of a few minutes of the mixture, 

 into which is dropped a 1 per cent solution of acetic acid. When the 

 mixture 110 longer becomes turbid, this shows that the caseinogen is entirely 

 decomposed. 



Hedin's Method (1904). After making a digestion with protein of any 

 type, the liquid in which the digestion has taken place is precipitated with 

 an equal volume of a solution consisting of tannic acid 70 grms., acetic acid 

 500 grms., sodium chloride 100 grms., water 1000 grms. ; this is filtered, and 

 the nitrogen of the filtrate estimated by Kjeldahl's method. 



The protein cleavage effected by trypsin is shown by the 

 work of Kiihne and his school (1867-93) to be very complicated. 

 Kiihne proved that it differs essentially from that effected by 

 pepsin, and may lead to a greater cleavage or disintegration of 

 the complex molecule of natural protein, independent of the 

 intestinal bacteria of putrefaction. The special text-books of 

 chemical physiology must be referred to for the study of all the 

 products into which proteins successively break up by the action 

 of trypsin. We must confine ourselves to stating that the first 

 direct products of cleavage are the secondary proteoses (deutero- 

 proteoses), and not primary proteoses (protoproteoses), as occurs in 

 pepsin digestion, and that the peptones are formed directly from 

 the deuteroproteoses. According to Kiihne pancreatic digestion 

 differs from gastric digestion, in that two kinds of peptones are 

 formed : a hemipeptone, which on the protracted action of trypsin 

 readily breaks up into leucine, tyrosine, aspartic acid, and other 

 products that are not exactly characterised, and an antipeptone 

 which resists the disintegrating action of trypsin, and can only 

 be decomposed into ammo-acids on boiling, with addition of dilute 

 sulphuric acid. The molecular aggregate of protein is thus com- 

 posed of two complex groups, the first of which splits up easily, 

 the other with difficulty ; both, however, contain nuclei of the 

 aromatic series as well as the fatty series. In the peptone of 

 gastric digestion, the two groups are still united, from which 



