ANATOMY AND PHYSIOLOGY 



the water or the animal or vegetable substance con- 

 tained the "germs" of these minute organisms, or else 

 that they were generated spontaneously. It was 

 known that boiling killed these animalcules, and Need- 

 ham agreed, therefore, that if he first heated the meat 

 or vegetables, and also the water containing them, and 

 then placed them in hermetically sealed jars if he 

 did this, and still the animalcules made their appear- 

 ance, it would be proof -positive that they had been 

 generated spontaneously. Accordingly he made nu- 

 merous experiments, always with the same results 

 that after a few days the water was found to swarm 

 with the microscopic creatures. The thing seemed 

 proven beyond question providing, of course, that 

 there had been no slips in the experiments. 



But Abbe Spallanzani thought that he detected 

 such slips in Needham's experiment. The possibility 

 of such slips might come in several ways : the contents 

 of the jar might not have been boiled for a sufficient 

 length of time to kill all the germs, or the air might not 

 have been excluded completely by the sealing process. 

 To cover both these contingencies, Spallanzani first 

 hermetically sealed the glass vessels and then boiled 

 them for three-quarters of an hour. Under these cir- 

 cumstances no animalcules ever made their appearance 

 a conclusive demonstration that rendered Need- 

 ham's grounds for his theory at once untenable. 2 



Allied to these studies of spontaneous generation 

 were Spallanzani's experiments and observations on 

 the physiological processes of generation among higher 

 animals. He experimented with frogs, tortoises, and 

 dogs ; and settled beyond question the function of the 



TOL. IT. 7 87 



