Appendix. 



that " the grave of each superstition which it lays is the womb 

 of a better birth." * 



I do not purpose, however, to enter into a discussion of the 

 arguments for or against the doctrine of spontaneous generation. 

 Such a task would require a series of lectures, instead of the 

 limited time allotted to me this evening, and it is doubtful, too, if 

 the resulting gain would be at all commensurate with the labor, 

 for it is a question which in the nature of things cannot.be argued 

 on the grounds of authority or of probability, but must rest on 

 experimental evidence alone. In the interpretation of this evi- 

 dence, however, we may with propriety accept the opinions of 

 those who by long training in scientific research are best quali- 

 fied to estimate such evidence at its real value. 



The history of the doctrine of spontaneous generation may 

 be conveniently divided into three epochs. The ist covers the 

 period from Aristotle, 325 B. C., to Redi, A. D. 1668. During 

 this epoch spontaneous generation was believed by all natural- 

 ists to be the common mode of the production of a very large 

 class of animals. The 26. epoch extends from the time of Redi 

 to the experiments of Sen wan n and Schultze, in 1836-7. This 

 epoch presents two phases, one relating to the generation of 

 animals visible to the naked eye, the other relating to the gener- 

 ation of infusorial animalcules invisible to the unaided eye. As 

 regards the first, spontaneous generation during this epoch " was 

 narrowed down to a rare and exceptional mode of the* reproduc- 

 tion of a few only of the most obscure species, and finally shown 

 to be untenable even for them."f The generation of a large 

 share of the entozoa was also explained during this period, and 

 they were removed from the class formerly believed to be pro- 

 duced by spontaneous generation. As regards the other phase 

 of this epoch, that relating to the infusoria, it may be said that 



*MAUDSI,EY: Body and Mind\ London, 1870; p. 111. 



t J. C. DALTON, M. D. : Spontaneous Generation, Neiv YorkMedicalJournal, 

 February, 1872. I am indebted to this admirable paper of Prof. Dalton's for 

 much of the material here made use of, and I desire now to express my 

 acknowledgments for such use in the instances where I have not given the 

 reference and page. 



