CHEMICAL DYNAMICS OF ANIMAL NUTRITION 137 



Serum. With reference to the influence of nutrition on the com- 

 position of the serum there are numerous researches, of which the most 

 recent are those of von Bergmann and Langstein. 1 The question as to 

 whether the products of tryptic digestion can be detected in the serum 

 has, in spite of the number of works on this subject, been by no means 

 definitely settled. Another question, which has given rise to consider- 

 able controversy, refers to the presence of albumoses and peptones in 

 blood (bodies giving the biuret reaction). These have been claimed 

 to be found by Emden and Knoop,* by Langstein, 3 and by Nolf. 4 Their 

 existence, on the other hand, has been denied by Abderhalden and 

 Oppenheimer, 5 and by Neumeister. 6 Now in Part II of these researches 

 (see p. 129) it has been shown that when albumens are coagulated in 

 concentrated solutions, the coagulum carries down with it a not in- 

 appreciable quantity of water soluble substances. On the other hand, 

 when coagulation is carried out in dilute solutions the precipitate is so 

 finely divided that satisfactory filtration is almost impossible. For 

 these reasons it is not surprising that contradictory results have been 

 obtained. 



In nearly every case in these researches, etc., the filtrates obtained 

 after coagulation, both alcoholic and aqueous, have been submitted to 

 the biuret reaction. In no single case was a positive result obtained. 



Neither the liver nor the serum was found to contain a trace of albumose 

 or peptone. With regard to the residual nitrogen of the sera the results 

 are evident from the following table : 



TABLE II 



