QUANTITATIVE DETERMINATION 143 



been effected in the course of demonstration, it may un- 

 doubtedly be said that nothing but an oxidation product can 

 be expected as the result. 



It may be, too, that a portion of the true urochrome may 

 undergo spontaneous decomposition in the urine with forma- 

 tion of its oxidation product. In any case we must regard, 

 not Dombrowski's urochrome, but Weiss 's so-called "true 

 urochrome ' ' as the native urinary yellow coloring material. 

 The attempt of the authors indicated to introduce a polemic 

 spice in their latest publication can have not the least influ- 

 ence upon the actual fact. 



Quantitative Determination of Oxyproteic Acids. 

 Our appreciation of the physiological role and signifi- 

 cance of the various substances of the group of oxyproteic 

 acids is of slow development. The reason for this is mainly 

 that as yet we are unable to overcome the technical difficul- 

 ties attending a quantitative determination of these sub- 

 stances. In discussing the elimination of the oxyproteic acids 

 and of neutral sulphur in cancerous disease (v. Vol. I of this 

 series, pp. 547-551, Chemistry of the Tissues) this fact was 

 fully presented. Eecently objection has been raised by F. 

 Erben 64 to the method of Ginsburg 65 for estimation of the 

 oxyproteic fraction in urine, that besides the oxyproteic 

 acids practically all the aminoacids are thrown down. There 

 is something, however, against the correctness of this charge 

 in the fact that Ginsburg has been unable to find more than 

 minute amounts of aminoacid nitrogen in his oxyproteic acid 

 fraction both by formol titration and, too, by Van Slyke's 

 method 66 (v. Vol. I of this series, p. 18, Chemistry of the 

 Tissues). Although Erben summarily characterizes Gins- 

 burg 's method as "useless," it should be observed that the 

 method, although (as already stated, v. Vol. I of this series, 



64 F. Erben (Vienna), Internal. Beitr. z. Pathol. u. Ther. d. Ernahrungs- 

 storungen, 2, 252, 1911. 



86 W. Ginsburg (Univers. Physiol. Instit., Vienna), Hofmeister'a Beitr., 

 10,411, 1907. 



88 Personal communication from W. Ginsburg, Halle a. d. Saale. 



