222 THE PHYSIOLOGY OF REPRODUCTION 



as far as the morula stage by depositing them in a salt solution 

 of such a concentration that they lose water. Sugar solutions 

 were also found to be effective. 1 



Various experiments have been tried with the object of 

 finding out whether ova could be fertilised by substances arti- 

 ficially extracted from spermatozoa, but so far without any 

 positive result. 2 Thus Gies attempted to obtain an enzyme 

 from spermatozoa, with a view to seeing if such a substance 

 would exert any influence on the unfertilised ovum, but his 

 experiments lent no support to the idea. 3 Pizon's 4 experiments 

 on the same question were also negative in result. (See p. 299.) 



Loeb 5 has discussed at some length the question as to 

 whether any idea can be formed regarding the nature of the 

 action of the spermatozoon in causing the ovum to develop. 

 He states his belief that " the essential effect of the sperma- 

 tozoon consists in the transformation of part of the proto- 

 plasmic or reserve material in the egg into the specific nuclein 

 or chromatin substance of the nucleus. In each nuclear 

 division one half of the mass of each original chromosome goes 

 into the nucleus of each of the two resulting cells. But during 

 the resting period which elapses until these nuclei are ready to 

 divide again, each chromosome grows to its original size, and 

 then a new division occurs. It is quite possible that the oxygen 

 which is required for the process of cell division is needed for 

 the synthesis of nuclein or chromatin substance. The fact that 

 the rate of development is influenced by temperature, in much 

 the same way as are chemical reactions, supports the idea given 

 above that the essential feature of fertilisation consists in the 

 starting or the acceleration of a chemical reaction which is 

 going on steadily in the egg. Loeb was disposed to conclude, 

 therefore, that the spermatozoon acts as a positive catalyser, 

 but further evidence has led him to reject this idea as im- 

 probable. He points out that, if it were correct, normal sea- 



1 Loeb, loc. cit. 



2 See Loeb, The Dynamics of Living Matter, New York, 1906. 



3 Gies, "Do Spermatozoa contain Enzyme having the Power of causing 

 Development of Mature Ova? " Amer. Jour, of Phys., vol. vi., 1901. 



4 Pizon, " Recherches sur une pratendue Ovulase des Spermatozoides," 

 C. R. de I'Acad. des Sciences, vol. cxli., 1905. 



5 Loeb { J:), loc. cit. 



