524 SCIENCE PROGRESS 



since 1882, the year in which Nencki published his researches 

 on this subject. 



The oxidation of uric acid and proteins was also investigated, 

 but the results were not very definite. Uric acid could be 

 oxidised only as far as uroxanic acid — 



QH.N.O, + O + 2H 2 = C 5 H 8 NA, 



Since that time much progress has been made in the study of 

 oxidation by means of enzymes, and the isolation of oxidases of 

 specific character from different organs. It is only necessary 

 to mention here the work of Bach and Chodat on the plant 

 oxidases, the work of Martin Jacoby on the different oxidases of 

 the liver, and the large series of researches on oxidases which 

 destroy the bodies of the purine group — with which work are 

 associated, amongst others, the names of Partridge and Jones, 

 Schittenhelm, and Burian. (See recent volumes of Hoppe- 

 Seyler's Zeitschrift.) 



We see, from the above summary, that Nencki's researches 

 dealing with putrefaction and fermentative action covered a 

 large field. On the morphological side they were concerned with 

 isolation of new species of bacteria and the preparation of pure 

 cultures. On the chemical side they were concerned with the 

 isolation of the various degradation products of proteins and 

 sugars, and with attempts to reproduce by purely chemical 

 methods reactions hitherto associated only with vital activity. 

 The results obtained have exerted a great influence in many 

 directions — in none more than in the furtherance of our know- 

 ledge of protein chemistry. 



III. The Formation of Urea in the Animal Body. 



In his first published work, carried out under the direction 

 of Schultzen, Nencki showed that if glycocoll and other amino- 

 acids be administered to an animal kept in nitrogenous equi- 

 librium, there is an increased output of nitrogen in the form of 

 urea. The administration of acid amides does not, however, 

 cause a like increase in urea formation. This indicated that 

 the ordinary products of tryptic digestion, such as glycocol, 

 leucine, etc., rapidly undergo decomposition with the elimi- 

 nation of nitrogen, which is excreted in the form of urea. 

 What is the mechanism of this urea formation, and what 

 organs are concerned with the chemical processes by means of 



