MELANIN COLOR FORMATION. 327 



Examples of other temporary or intermittent oxidative powers 

 might be much extended to include cases of glycosuria, cys- 

 tinuria, purin metabolism, etc. I shall not discuss these cases 

 which have only an indirect bearing on our question of tyrosin 

 oxidation. It is, however, of some interest to state that it has 

 become evident through the work of Abderhalden and Schitten- 

 helm ('05), Garrod and Hurtley ('06), and others, that the body 

 may possess a low oxidizing power for several different protei)i 

 constituents at the same time ; as, for example, in some cases of 

 cystinu'ria, when diamines, tyrosin, lysin, etc., in addition to cys- 

 tin, pass through the body unoxidized and appear as such in the 

 urine. 



The known facts of abnormal pigmentations deserve a larger 

 share of attention than they receive here. They are mentioned 

 chiefly to direct attention to a field of facts that are quite com- 

 pletely ignored in our theories of the heredity of color. 



In the condition known as ochronosis, certain cartilages (e. g., 

 those of the ear) and connective tissues become pigmented. The 

 work of Albrecht ('02), Osier ('04), Pick ('06), and others, make 

 it certain that ochronosis is a form of melanotic pigmentation, 

 and that it is not uncommonly associated with melanuria, or 

 alkaptonuria and even with the pigmentation of the sclerotics 

 and skin (Osier). Similarly, in Addisori 's disease there is de- 

 posited in the skin a pigment which, according to Pforringer 

 ('oo) differs from that produced normally only in quantity and 

 not in origin or composition. It is well known too that nerve 

 lesions are often accompanied by pathological pigmentation of 

 the skin. 1 



A word in regard to melanotic tumors. These are known to 

 occur particularly in white horses. The amount of melanin 

 produced is often very great. Abel and Davis ('96) estimate the 

 melanin of the entire skin of a negro at I gram, whereas Nencki 

 and Berdez ('85) found 300 grams of melanin in a sarcomatous 

 liver, and estimate that the entire body contained 500 grams. 



These several facts from pathology are significant in that they 

 indicate that/<?r the building of any melanin at all, the actual local 

 conditions of the organism, or the organ, have a role to play that 



1 See resume by Schmidt, Ergeb. Jer Pathol., Bd. III., Abt. I, p. 551, 1896. 



