STUDY OF FERTILIZATION 421 



active unit is invariably accompanied by an electrical disturb- 

 ance ; and there seems good evidence for the belief that the 

 electrical change is the essential condition of activity. When 

 an inactive unit comes into contact with an active unit, an 

 electro-motive force is established between the two ; the active 

 unit is electro-negative to the inactive unit, and if activation 

 of the latter occurs, the state of negativity is not restricted to 

 the region of contact but spreads from it all over the originally 

 inactive surface. Such facts are, of course, well known in the 

 case of fibres in the same muscle, but Kiihne (18) showed that 

 the action current of one muscle could stimulate another muscle 

 if the two were in close electrical contact. Now the E.M.F. 

 set up between two cells in contact depends on, and is an expres- 

 sion of, the difference in the activity of the two units ; the 

 greater the difference in activity the greater is the E.M.F. set 

 up on contact. 



In the opinion of the writer an application of the above 

 principles to the problem of fertilization is not without value. 

 In the unfertilized egg metabolic activity is reduced to a 

 minimum, and unless fertilization takes place the cell dies with- 

 out any recovery from its inert condition. The spermatozoon, 

 on the other hand, is radically different : it is exceedingly 

 active and metabolism proceeds at a rapid rate (Cohn, 3). 

 When the two cells come into contact it seems legitimate to 

 conclude that an E.M.F. will be set up between the two, and if 

 the conditions be right it is to be expected that some form 

 of activity will be induced in the inert egg. If the process of 

 activation be analogous to that of other cells, then the egg will 

 be activated whenever the E.M.F. set up by contact with 

 a spermatozoon reaches a certain minimum value in a minimum 

 time. It is, therefore, not surprising to find that a certain 

 minimum of activity on the part of a spermatozoon is necessary 

 for fertilization. Mobility and proximity of the egg are not 

 sufficient — a fact difficult to explain on any chemical concep- 

 tion ; there must be a definite and rather high degree of 

 activity on the part of the sperm, and this degree of activity 

 di-ffers between individual spermatozoa. Glaser (7) observed 



