558 WASTE-PRODUCTS 



for this purpose nor are the proteins of the blood broken down to fur- 

 nish glycocoll, for the ratio of albumins (containing no glycocoll) to 

 globulins in the blood-serum remains unaltered by benzoic-acid 

 administration. 



In the metabolism of birds, Ornithine, or diami no valeric acid plays 



CH 2 (NH 2 )CH 2 .CH2.CH(NH2)COOH 



the part which is taken by glycocoll in the metabolism of mammals, 

 or, at all events, to the extent of being the substance utilized to 

 detoxicate and eliminate benzoic acid. The conjugated acid which 

 appears in the urine of birds when benzoic acid is administered to 

 them is Ornithuric Acid, which splits into benzoic acid and ornithine 

 when it is hydrolyzed. 



AROMATIC OXYACIDS. 



The putrefaction of proteins in the intestine results in the formation 

 of Paraoxyphenylacetic Acid and Paraoxyphenylpropionic Acid as inter- 

 mediate stages in the decomposition of tyrosine, and they pass in 

 small amounts unchanged into the urine. 



It has been observed, from the middle ages, that human urine in 

 certain very rare instances may regularly darken on exposure to air 

 and ultimately turn black. The individuals exhibiting this peculiarity, 

 which is designated Alcaptonuria, are very rare, and yet the condition 

 constitutes a definite peculiarity of metabolism which has often been 

 described, and has been very carefully investigated. The darkening 

 is due to the spontaneous oxidation of dioxyphenyl acetic acid or 

 Homogentisic Acid: 



CH 



/\ . ; . :i:;i 



HC COH 



HOC CH 



CH 



CH 2 

 I 

 COOH 



which is a constituent of the urine of these persons. The individuals 

 who display this peculiarity do not appear to suffer any inconvenience 

 from it, and cases only reach the physician through the alarm created 

 by the extraordinary appearance of the urine after standing, or by 

 failure to secure an insurance-policy, for dioxyphenyl acetic acid is a 

 reducing-substance and may be reported by a physician who is unfa- 

 miliar with the typical indications of the disease, as glycosuria. The 



