28 BIOLOGY: GENERAL AND MEDICAL 



for a time. When the chamber thus prepared was stood 

 away, it was found that life rarely developed in the con- 

 tents of the tubes and that no putrefaction took place. 

 Thus Tyndall confirmed the work of Pasteur who in the 

 meantime had been busily engaged in showing that there 

 were " organized corpuscles" in the atmosphere the 

 "floating matter" of Tyndall which when admitted to 

 the infusions caused them to putrefy. 



Cohn had engaged in morphological studies of the 

 bacteria and other low forms of life, and had discovered 

 that many of them, under appropriate conditions, pass 

 into a resting or spore stage. In many of the rod-shaped 

 organisms a spot appeared in the rod, grew larger and 

 larger, and became surrounded by a capsule. While 

 this was perfecting its development, the rod in which it 

 formed began to degenerate and eventually set it free. 

 Thus there came into being a minute body a spore. 

 Further study of the spores showed that they abounded 

 in the atmosphere and that many of them could endure 

 temperatures higher than that of boiling water. It now 

 seems clear that it was through the entrance of such 

 spores into the infusions, their endurance of the tempera- 

 tures to which the fluids were subjected during boiling, 

 and their subsequent germination that the appearance 

 of life in the fluids was to be referred. 



Thus Harvey's law omne vivum ex ovo which had long 

 been accepted with reference to the higher beings became 

 applicable to the lowest organisms in the modified form 

 omne vivum ex vivo, and the doctrine of the spontaneous 

 generation of life might be supposed to have received its 

 death blow. The evidences thus collected were subse- 

 quently investigated by a great number of workers, by 

 a great variety of methods, but with uniform results 

 and at present almost every scientific mind is satisfied 

 that life in the forms in which we now know it is never 

 spontaneously evolved. 



However, it remained to explain how, if all life de- 

 scended from antecedent life, living things originally 



