4 THE ROYAL SOCIETY OF CANADA 



Tercul in 1872 and later Béchamp insisted that souring was due 

 to minute living bodies (microzoma) in the milk, which were derived 

 from the cow, and were capable of developing into the organisms de- 

 scribed by Pasteur. These views, however, were soon discredited. 



So far, however, nothing had been found out as to the source of 

 these organisms in the milk. Did they get into milk from the cow 

 or was the normal souring due to some enzyme secreted by the animal ? 

 Or was it possible that these organisms came from the air ? 



Rallier (1866), believed that micrococci and yeasts were simply 

 stages in the life history of the higher fungi; thus, he considered 

 micrococci as the spores of one of the higher plants and believed that 

 these could and did pass into the blood and therefore that the organ- 

 isms in milk came from the cow. Schroder was of the same opinion 

 that the organisms came from the udder and were the normal con- 

 stituents of milk. Hoppe-Seyler (1859) held the view that souring 

 was due to some enzyme secreted by the cow and that milk contained 

 a ferment which was destroyed by heat but reactivated by oxygen. 

 Even in 1881 whilst admitting that micro-organisms might hasten 

 the process, he was of the opinion that souring was normally caused 

 by an unorganized ferment produced by the cow. 



The proof of the external source of infection was first made by 

 Robert Hall in 1874 but before outlining his results, mention must be 

 made of the work of Lister published in 1873 and 1877. The earlier 

 paper described the microscopical examination of (sour) milk in which 

 he saw many bacteria, some singly and others in chains. A drop of 

 this milk was transferred to sterilized media, such as beef infusion, 

 milk, urine, etc., and was followed by the development of different 

 media. After several subcultures and cross inoculations he reintro- 

 duced them into sterile milk and found that the milk soured normally. 

 He concluded that he had only one organism, changed in shape and 

 function by growth in the various media employed. To this organism 

 he gave the name of Bacterium lactis. Later, however. Lister 

 noticed the error of having impure cultures to start with and he 

 devised the first method of obtaining a pure culture of a bacterial 

 organism, a method we know now as that of high dilutions and which 

 has in these later days been improved and used with success. 



Lister by this means obtained one of the first pure cultures of 

 the lactic acid organism, and was enabled to study it and ascertain 

 its permanent specific characteristics. Another series of his experi- 

 ments consisted of exposing sterile milk in various places — in his 

 laboratory, in the open air, in a stable, etc., and he found that milk so 

 exposed would ferment but would not necessarily undergo the typical 



