January 14, 1916] 



SCIENCE 



43 



mals. In making these experiments lie 

 thought he found cases in which seminal 

 fluid devoid of spermatozoa would fertilize 

 and thus fell into the error, which he was 

 so ready to accept from his opposition to 

 the spermatists, that the fluid medium of 

 the seminal fluid was the fertilii;ing sub- 

 stance. He also investigated the condi- 

 tions of successful insemination, with ref- 

 erence to the duration of fertilizing power, 

 exposure to various chemicals, to heat, etc. 

 The amount of dilution of which the semi- 

 nal fluid was capable was also carefully in- 

 vestigated. By experiment he excluded the 

 idea that fertilization might be an eflrect of 

 an emanation, or vapor arising from the 

 sperm. 



He concluded that the seminal fluid acted 

 by accelerating the vital processes; it en- 

 ters the body through pores, and stimu- 

 lates the action of the heart. This idea 

 offered no difficulty to one who believed 

 that the organism was preformed in the 

 ovum, and it was supported by the observa- 

 tion that the beating of the heart was the 

 flrst observable movement of the embryo. 

 Bonnet suggested to him the problem, if 

 the spermatic fluid might stimulate the 

 heart of the embryo in the process of fer- 

 tilization, why might not other fluids pro- 

 duce the same effect ? He was thus led to 

 attempt the first experiments on artificial 

 parthenogenesis ; he tried to start the devel- 

 opment of eggs by electricity, by the action 

 of extracts of all the various organs, by 

 vinegar, dilute alcohol, lemon juice, and 

 other substances, all without effect. 



It is interesting to see how his experi- 

 ments led to hypotheses and these, even 

 though wrong, to further experiments, some 

 of which, like his experiments on artificial 

 parthenogenesis, were not taken up again 

 in a fruitful way for over a century. 



His final experiments are those so often 

 qiioted as furnishing the proof that fertiliz- 



ing power resides in the spermatozoon. He 

 showed that, if diluted sperm be filtered 

 through a sufficient number of layers of 

 filter paper, the filtrate has no fertilizing 

 power, whereas the residue washed off the 

 filter paper will fertilize. But he did not 

 himself draw the correct conclusion; he 

 says the experiment proves ' ' that filtration 

 removes from spermatized water its fertil- 

 izing power, inasmuch as the seminal fluid 

 which was contained in it remains on the 

 filter papers, from which one can extract 

 it by pressing them. " It is perfectly clear 

 that Spall anzani himself never held that 

 the spermatozoa themselves were the fertil- 

 izing agents, but, on the contrary, he con- 

 tests this idea strongly as leading to sper- 

 matist delusions. 



1800-1870.— Aitev Spallanzani there was 

 no real advance in the theory of fertiliza- 

 tion until the publication of Prevost et 

 Dumas' "New Theory of Reproduction" in 

 1824. They observed that young animals 

 incapable of breeding, old animals beyond 

 the breeding stage, the infertile mule, and 

 birds outside of the breeding season possess 

 no spermatozoa, and they conclude that 

 these facts "sufficiently prove the impor- 

 tance of the animalcules, and show that 

 there exists an intimate relationship be- 

 tween their presence in the reproductive 

 organs and the fertilizing power of the 

 animal." In a long series of experiments 

 they investigated the conditions of ferti- 

 lization in frogs : all conditions that destroy 

 the animalcules destroy also the fertilizing 

 power of sperm suspensions ; the filtrate of 

 a sperm suspension devoid of spermatozoa 

 will not fertilize ; the redissolved residue of 

 a suspension evaporated to dryness will not 

 fertilize, etc. ; the number of eggs fertilized 

 is always less than the number of animal- 

 cules employed. So that they came to the 

 conclusion that "the prolific principle 

 resides in the spermatic animalcules." 



