362 



SCIENCE. 



[N. S. Vol. XV. No. 375. 



of the milk below. The increased resist- 

 ance is not due to lowered temperature at 

 surface, as was shown by removing mem- 

 brane and placing same in water, when it 

 sunk to the bottom. The protection there- 

 fore afforded the bacteria is due to the na- 

 ture of the membrane itself, preventing the 

 heat from exercising the usual effect. 



The Comparative Grotvth of Bacteria in 

 Milk: H. W. Conn, Wesleyan Univer- 

 sity, Middletown, Ct. 

 This paper described a series of experi- 

 ments, the design of which was to deter- 

 mine what species of bacteria develop in 

 milk during the first twenty- four hours and 

 what species disappear. The general pur- 

 pose of the experiments was to determine 

 as far as possible the relation of milk bac- 

 teria to the healthfulness of milk. The con- 

 clusions presented by the paper were as 

 follows: (1) Milk freshly drawn from the 

 cow contains a large variety of bacteria. 

 (2) For the first six hours and sometimes 

 more, there is no increase in the number of 

 bacteria, even when the milk is kept at 

 70°. On the contrary, there is commonly 

 a decrease due to what has been called 

 the ' germicide power ' of milk. ( 3 ) In the 

 fresh milk the largest number of bacteria 

 are streptococci, which come, in most cases, 

 directly from the udder of the cow. (4) 

 During the first forty-eight hours there is 

 a very great increase in the number of 

 bacteria, but the number present after one 

 or two days' growth is quite independent 

 of the number present at the start. In 

 many cases milk, which when fresh con- 

 tained a small number of bacteria, at 

 the end of forty-eight hours contained a 

 number far greater than other samples of 

 milk which at the outset had a larger num- 

 ber of bacteria present. (5) During the 

 first forty-eight hours there is a consider- 

 able increase in the number of strepto- 

 cocci, followed by their decrease and final 



disappearance. (6) At the outset the num- 

 ber of lactic bacteria is extremely small, 

 so small as, at times, quite to escape obser- 

 vation. (7) These lactic bacteria are, at 

 least in the series of experiments described, 

 derived from sources external to the cow 

 and never, or rarely, from the milk ducts. 

 (8) The lactic bacteria, though very few 

 in number at the outset, increase far more 

 rapidly than any other types, so that with- 

 in twenty-four hours they are commonly 

 in the majority, and by the end of forty- 

 eight hours they commonly comprise con- 

 siderably over ninety per cent, of all the 

 bacteria present. 



Rusty Spot in Cheddar Cheese: H. A. 

 Haeding and L. A. Rogers, N. Y. Agri- 

 cultural Experiment Station, Geneva, 

 N. Y. 



Rusty spot is a bacterial trouble of Ched- 

 dar cheese characterized by reddish-yellow 

 discolorations scattered in points or 

 blotches throughout the mass. The cheese 

 does not become poisonous and the flavor 

 is not affected, but the market price is re- 

 duced on account of the unusual appear- 

 ance. This trouble is confined to a few 

 factories, but a considerable part of their 

 output is affected. A short, plump, causal 

 bacillus was isolated by Cornell in 1898 

 and called Bacillus rudensis. By the addi- 

 tion of pure cultures to vats of milk he 

 was able to reproduce the discoloration in 

 the resulting cheese. In practice, the main 

 source of trouble is the bacterial growth 

 upon the factory utensils. However, there 

 are often outside foci in connection with 

 the dairies, capable of reseeding the fac- 

 tory after it has been once freed from the 

 infection by a careful cleaning and disin- 

 fection. The direct application of steam 

 to all the factory utensils on three days 

 each week was tried in three infected fac- 

 tories during the past season. This is 

 most easily accomplished by placing all 



