1904.] Tyrosinases in the Skins of Pigmented Vertebrates. 313 



insoluble in mineral acids. Further experiments are in progress, on a 

 larger scale, to endeavour to produce enough for a thorough analysis. 



Summary. 



An extract can be made from the skins of certain pigmented 

 animals (rabbits, rats, guinea-pigs and chickens), which will act upon 

 tyrosin and produce a pigmented substance. This action suggests 

 the presence of a tyrosinase in the skins of these animals. 



The action of the tyrosinase is destroyed by boiling, does not take 

 place in the cold, is delayed by time, requires a temperature of about 

 37 C., and also the presence of an activating substance such as 

 ferrous sulphate to start it. 



The coloured substances produced are in accordance with the colour 

 of the animals used. Black substances are obtained, when animals 

 with black pigment in their skins are used, and yellow substance, 

 when the skin contains the orange pigment. The coloured substances 

 are soluble in alkalis, but insoluble in acids. 



In conclusion, I take this opportunity to express my gratitude to 

 Dr. Hopkins, to whom I am indebted for help and advice in the 

 foregoing experiments. 



LITERATUKE. 



(1) Bateson. ' Proceedings of the Zoological Society,' 1903. 



(2) v. Fiirth u. Schneider. ' Beitr. z. Chem., Phys., u. Path.,' Bd. 1. 



(3) Ducceschi. ' Kendiconti della B. Accad. dei Lincei,' vol. 2. 



' Archivio di Fisiologia,' vol. 1. 



(4) Cuenot. ' Arch. d. Zool. Exper. et G-en., Notes et Eevue,' vol. 1. 





