EXCHANGE OF MATEEIAL 



33 



certain other organic substances, some of which are formed during 

 the process of digestion in the alimentary canal, while others are 

 almost always found mingled with our food. Albumoses, peptones, 

 amino-acids, fatty acids, and glycerine belong to the former class ; 

 gelatine, alcoholic beverages, and the so-called condiments to the 

 latter. 



(a) In the course of our study -of the chemical processes of 

 digestion, both gastric and intestinal (Vol. II. Chaps. III. and 

 IV.), we saw that protein substances are resolved into many 

 different products, protoalbumose, deuteroalbumose, hemipeptones, 

 antipeptones, amino-acids. It will now be of interest to ascertain 

 the nutritive values of these substances in relation to their 

 different chemical constitution. 



The first researches undertaken by Plosz, Maly, Adamkiewicz 

 (1874-77-78) were made with the so-called peptone of commerce, 

 which is a mixture of the different products of protein digestion. 

 These researches, however, seem to prove that this compound of 

 different digestive products is of the same nutritive value as the 

 genuine protein of the ordinary diet. For instance, Adamkiewicz 

 gave to a fasting dog, which weighed about 20 kgrms., and was 

 losing on an average 3'75 grms. of nitrogen per day, 50 grms. of 

 peptone containing 7'75 of nitrogen, and the animal discharged 

 an average of 8'52 grms. of nitrogen. When 100 grms. of 

 fat were added to the peptone, it only discharged 5 - 74 grms. of 

 nitrogen, so that the intake and output of nitrogen were almost 

 equal. 



Pollitzer (1885) in his researches made use of amphopeptone, 

 protoalbumose, and deuteroalbumose, isolated according to Kiihne's 

 method, and found that all these three products are of the same 

 nutritive value as a corresponding quantity of meat, as will be 

 seen from the following table : 



Ellinger in 1896 investigated the nutritive value of the 

 mixture resulting from the digestion of the pancreas (glandular 

 peptone), which Kiihne considers to be composed mainly of anti- 

 peptone, but which contains other final products of digestion, and 

 confirmed the results obtained by Pollitzer. 



The more recent researches made by Blum in 1900 were 

 VOL. v D 



