THE HISTORY OF BACTERIOLOGY. 59 



firmed these observations and made many new ones in connection with the 

 behaviour of milk, egg albumen, vegetable substances kept under certain 

 conditions, and pieces of organs from freshly-killed animals to which 

 organisms from the external air were not allowed to gain access. 



It seemed as though the adherents of abiogenesis had not 

 a leg left on which to stand ; but owing to the fact that 

 certain organisms, especially when contained in such media 

 as milk and cheese, withstand the action of very considerable 

 heat, they still contested every^ inch of ground, though their 

 foothold was being gradually but surely cut away from 

 beneath them. Milk, which was one of the strongholds of 

 the abiogenists, was first sterilized, with absolute certainty, 

 by Schroeder, who attained his end by subjecting the fluid 

 for a considerable time to a temperature of ioo° C, and then 

 by Pasteur, who heated it to iio° C, for a short time only. 

 Cheese still remained to them, and as late as 1872 Bastian 

 placed a small piece of this substance in an infusion of white 

 turnip which had been filtered and carefully sterilized. This 

 was then boiled in a flask for ten minutes, and whilst still 

 boiling was hermetically sealed ; at the end of three days 

 countless living organisms were produced, as Bastian held, 

 from non-living albuminoid material ; but Cohn, repeating 

 the experiment, explained that the resting spores or resistant 

 germs were enclosed in the substance of the cheese, and that 

 they were thus able to resist the high temperature to which 

 the outer surface of the cheese, but not its centre, was 

 exposed. Duclaux's later experiments with the Tyrothrix 

 of cheese, which resists the action of a very high temperature 

 for a considerable time, also helps to explain Bastian's results. 

 The matter has now been set at rest, and it is an accepted 

 belief that bacteria or microbes, as these lowly organized 

 forms are now called, may be destroyed by heat and by 

 certain chemical reagents, and that when once destroyed in 

 any medium, no other organisms can rise from their ashes, 

 the medium remaining perfectly free from putrefactive 

 changes until fresh germs are introduced from without. 

 Harvey's famous dictum, omne vivum ex ovo, has thus come 

 to have a far wider meaning than that which he originally 

 attached to it. The triumphs of surgery, of preventive 

 inoculation, of hygiene in relation to specific infective 

 diseases, of preservation of food, have had their origin in 

 the knowledge gained during the battle which waged round 



