398 Bulletin 165. 



route was used for butter making, the deep setting system of 

 creaming being used. The cream on the surface of the cans of 

 milk which stood in water at a temperature of from 45° to 50° F. 

 (7°-io° C.) became viscid in from twenty-four to forty-eight 

 hours after setting, so that it would adhere to a table fork, 

 stringing out in a ropy mass. The frontispiece of this bulletin 

 illustrates the tj'pical behavior of the cream. The viscosity was 

 more marked in the surface layer of the milk, and hence in the 

 cream. It is for this reason that the trouble is incorrectly 

 regarded as a fault peculiar to cream. No complaint was heard 

 from those customers who consumed the milk within a few hours. 

 Some of them, however, kept the milk until the following morn- 

 ing when the cream would be ropy. 



A bacteriologic examination of the ropy cream revealed the 

 presence of Bacillus ladis viscosiis. After isolating from the 

 viscid cream an organism which invariably produced the ropiness 

 in milk (or cream) when inoculated with it, further work to 

 determine the distribution of this organism in nature and to find 

 out through what channels the milk became infected seemed 

 highly desirable. To accomplish this it was proposed to collect 

 samples of the milk at each step in the processes to which it 

 was subjected between the cows' udders and the deep setting cans 

 where the ropiness becomes manifest. The fact that the organism 

 grows in milk at a temperature of 54°F. (i2°C.) and produces 

 ropiness in a few days, was a valuable aid in the search since 

 such a low temperature will prevent the rapid multiplication of 

 most species of bacteria in milk. If the samples collected are 

 kept at room temperature, there is no assurance that Bacillus 

 lactis viscosus can be detected among the other bacteria present. 

 By lowering the temperature the growth of most microorganisms 

 is checked, without seriously hindering the multiplication of the 

 one causing the ropiness. It was just this condition in the 

 creamery which enabled that species to assert its presence in the 

 deep setting cans. 



In taking samples of milk from each cow, the udders and teats 

 were moistened with a weak solution of carbolic acid, this being 

 the only safeguard taken to prevent the access of dust. Glass 

 milk bottles w^ere scalded and kept sealed with paper covers, 



