166 AGRICULTURAL BACTERIOLOGY 



It is believed that milk in which a considerable amount 

 of bacterial growth has occurred is less healthful that milk 

 of lower bacterial content. There is no reason to believe 

 that the organisms of the Bact. lactis acidi group injure 

 the healthf ulness in any way, no matter how much they 

 may have grown in it. There are many other groups of 

 bacteria constantly present in milk for which such an asser- 

 tion can not be made with assurance. Among these may 

 be classed the liquefying bacteria and those of the B. coli- 

 aerogenes group. 



Infant mortality. It is thought that the milk supply has 

 much to do with the high death rate of young children. 

 In some American cities more than 40 per cent, of the 

 children die before they reach one year of age. The 

 greater number of these are fed on some substitute for 

 mothers' milk, cows' milk being most frequently used. It 

 is claimed that if the milk were of better quality, if it con- 

 tained less bacteria, and had undergone less decomposition, 

 a great decrease in the death rate of artificially fed chil- 

 dren would be noted. It is certain that the most powerful 

 factor concerned in the great improvement of market milk 

 that has taken place in recent years has been the effort to 

 reduce the high rate of infant mortality. 



Poisonous foods. Substances that are very poisonous 

 when swallowed are formed by certain bacteria, the most 

 prominent of which is B. botulinus, a spore-forming anaer- 

 obic organism. The organism received its name from the 

 fact that it was first found in sausage (Latin, botulus, sau- 

 sage). For some time it was thought that only foods of 

 animal origin permitted the growth of this organism. More 

 recently, cases of botulinus poisoning have been traced to 

 various vegetables. In almost all instances the trouble has 

 been caused by the use of canned rather than fresh mater- 

 ials. The spores of the organism enable it to resist the 



