FECUNDATION. 351 



though a portion had been taken off with a sharp instru- 

 ment. The janitor stated that his wife, during her preg- 

 nancy, dreamed that she saw a man with a similar deformity. 

 This dream was very vivid, and she immediately related it to 

 her husband. They both believed that this was the cause of 

 the deformity of the child. 1 It will be remarked, however, 

 that this case rests on the evidence of the husband, and was 

 not mentioned to Prof. Dalton until after the child was born. 

 As such, it might be rejected as one of those instances in 

 which the explanation is a statement following a knowledge 

 of the deformity. Still, we ourselves know the husband to 

 be an intelligent man, and believe that his statement of the 

 circumstances is reliable. 



Union of the Male with the Female Element of Genera- 

 tion. The first important step in our positive knowledge of 

 the mechanism of fecundation was the discovery of the sper- 

 matozoids, in 1677, to which we have already referred ; the 

 second was the demonstration, by Spallanzani, in his experi- 

 ments upon artificial fecundation, that when the seminal fluid 

 is carefully filtered, the liquid which passes through has no 

 fecundating properties, the male element remaining on the 

 filter ; and the third was the demonstration of the presence 

 of spermatozoids within the vitelline membrane, showing 

 that fecundation consists in a direct union of the male with 

 the female element. 



Spallanzani filtered the seminal fluid of frogs, and found 

 that its fecundating properties were diminished in propor- 

 tion as the filtration was thorough, and that the fluid was in- 

 active when filtered through six or seven papers ; but, when 

 the substance remaining on the filters was taken and mixed 

 with water, this readily fecundated ova. Spallanzani also 

 made a number of interesting experiments upon artificial fe- 

 cundation in mammals. In connection with Prof. Rossi, he 

 injected seminal fluid from a dog into a bitch in heat, on 



1 Communication from Prof. Dalton. 

 153 



