QUANTITATIVE ESTIMATION OF HIPPURIC ACID 113 



CH 2 .COOH) is nontoxic. This suggests the thought that 

 perhaps in another synthetic process which takes place in the 

 body, between glycocoll and cholic acid, with formation of 

 the glycocholic acid of the bile (Vol. I of this series, p. 306, 

 Chemistry of the Tissues), glycocoll may be playing the part 

 of a detoxifying agent. Benzoic acid introduced into living 

 birds is, however, not rendered harmless by glycocoll; in 

 birds another cleavage product of the protein molecule takes 

 its place, as pointed out by the celebrated Konigsberg phar- 

 macologist, M. Jaffe (recently deceased), viz.: ornithin 



which, as is known, originates from cleavage of 



fCH 2 NH,\ 



CH, 

 CH 2 



CN.NH 2 

 COOH 



arginin (Vol. I of this series, p. 10, Chemistry of the Tis- 

 sues). 44 This appears in the urine as a dibenzoyl compound, 

 ornithuric acid : 



CH 2 .NH CH 2 CH 2 CH.NH COOH 

 CO.CH 6 CO.CeH 5 . 



Quantitative Estimation of Hippuric Acid. Before 

 leaving this part of the subject reference should be 

 made to the method of quantitative determination of hip- 

 puric acid, a substance of decided importance physiologi- 

 cally. The hippuric acid in an animal fluid may be estimated 

 as such ; or its glycocoll may be determined ; or the benzoic 

 acid. The first of these plans is followed in the method of 

 Bunge and Schmiedeberg, in which the hippuric acid is 

 extracted by acetic ether from urine, purified by passing 

 through animal charcoal, and weighed. Henriques and 

 Sorensen employ their method of f ormol titration to estimate 

 the glycocoll separated out from the hippuric acid. 



44 In the text referred to in the formula for ornithin an unfortunate typo- 

 graphical error occurs, in that one CH-t group too many is shown. 



8 



