THE HISTORY OF BACTERIOLOGY. 55 



were Hartsoeker, Reaumur, and Joblot, considered, though 

 they had no great amount of evidence to adduce in support 

 of their theory, that bacteria were the progeny of minute 

 organisms which were present in myriads in the air, from 

 which they were deposited on fruits, plants, and other matter, 

 whence they made their way into the various infusions 

 prepared from them. In this country a prophet arose in the 

 person of Dr. Needham, who was really the first to suggest 

 an attempted solution of the question by a theory of abioge- 

 nesis, or spontaneous generation. Needham at first thought 

 that these vibriones, or "plant animals," as he called them, 

 arose from plants by special vegetative power, and that from 

 the plant-animals, by a process of evolutionary accretions, 

 other organisms again arose. He tried to prove, by boiling 

 a beef infusion and keeping it and allowing it to putrefy 

 in a well-stoppered bottle (a most scientific method), that 

 these zoophytes could not owe their origin to germs which 

 outside insects or organisms had brought into the infusion, 

 as he considered that the boiling should have destroyed the 

 germs originally in the fluid, and as no new germs could, he 

 thought, make their way into the closely-stoppered vessel, 

 the resulting organisms must be the result of the action of 

 a special vegetative force. This apparently logical and 

 fascinating theory was accepted by many whose names had 

 great weight in the scientific world. Needham's observations 

 were repeated time after time with the same results, and his 

 theory met with wide acceptance. 



To very critical minds it appeared, however, that these 

 experiments of Needham's left loopholes for the inser- 

 tion of other explanations than those which he gave, and 

 Bonnet, of Geneva, suggested that the vessels used by 

 Needham were not hermetically sealed, that an almost 

 invisible opening would be quite sufficient to serve as a 

 means of entrance to organisms so minute as those with 

 which he was dealing, and that on the other hand there was 

 a possibility that the germs were so far resistant to increase 

 of temperature that they might live through a short period 

 (a few minutes only) of treatment with boiling water. Abbot 

 Spallanzani followed up, by his wonderful experiments, the 

 theoretical criticism of Bonnet. After convincing himself 

 that organisms did actually develop in unboiled infusions 

 even when the outer air was rigorously excluded, he argued 



