Optimum Temperature of Salicin Hydrolysis, etc. 245 



perfectly capable of development. The eggs of (b), however, had neither 

 developed nor had they undergone cytolysis. They had remained clear, 

 transparent, and unaltered, although they were surrounded by forests of 

 spermatozoa which had failed to enter them. The eggs of the portion (c) 

 had likewise remained clear and unaltered. 



It is therefore proved that the entry of a foreign spermatozoon into an 

 egg may cause its death by producing cytolysis, and the enormous produc- 

 tion of mesenchyme which takes place in those few hybrid eggs which 

 do develop is in all probability a phenomenon of the same kind as cytolysis, 

 which is after all only a premature and exaggerated fragmentation of the 

 cytoplasm. But an egg can become totally unreceptive to foreign 

 spermatozoa, whilst it is still capable of receiving the spermatozoa belonging 

 to its own species and of undergoing normal development, and thus two 

 causes of sterility when distinct species are crossed are unmasked, viz., 

 either (a) the egg refuses to receive the foreign spermatozoon at all or (b) it 

 receives it and undergoes cytolysis in consequence. 



The Optimum Temperature of Salicin Hydrolysis by Enzyme 

 Action is Independent of the Concentrations of Substrate and 

 Enzyme. 



By Arthur Compton, B.A., M.B., RILL, Imperial Cancer Research Fund. 



(Communicated by Sir J. E. Bradford, K.C.M.G., Sec. R.S. Received 

 October 14, — Read December 4, 1913.) 



The object of the present investigation is to ascertain the influence, if any, 

 on the optimum temperature — temperature of greatest activity — of an 

 enzyme, of the concentration, on the one hand, of the substrate, and, on the 

 other, of the enzyme. The investigation, involving two variables, presents 

 three cases for consideration, according as the concentration of the substrate 

 and the concentration of the enzyme are varied separately or together. An 

 account is given of the results obtained with the enzyme or enzymic 

 function, present in sweet-almond emulsin, which hydrolyses the glucoside 

 salicin with the production of equimolecular quantities of glucose and 

 saligenin. A commercial specimen of Merck's emulsin was used, while the 

 purity of the salicin employed was ascertained by determining its melting 

 point (200-5°) and its optical activity ([«]» = — 62-'7 ). 



