INFECTION FROM MILK. 43 



fish, oysters), or they may be contaminated by 

 unclean and improper preservation later. The 

 symptoms caused by their ingestion are actual in- 

 fections in some instances (as with Bacillus enter- 

 itidis), whereas in others the condition may be one 

 of intoxication by the products of saprophytic ac- 

 tivity (Bacillus botulinus) . 



Some vegetables contain highly poisonous alka- 

 loids and toxins, which rarely find a place in dis- 

 ease. Some of them have been of great value in 

 the experimental study of toxins and antitoxins. 

 (See table at close of Chapter I.) 



3. Animals are sometimes subject to infection Animals. 

 by microbes which are also pathogenic for man, 

 transmission taking place through the consump- 

 tion of diseased meat or milk, or through direct 

 or indirect contact, through wounds, or by the 

 bites of insects. 



In bovine tuberculosis the udder is frequently 

 involved, and in such cases large quantities of the 

 bacilli are excreted by the milk. Although the 

 virulence of the bovine bacillus for man may not 

 be so great as that of human tuberculosis, it is 

 now well established that it often infects man, 

 perhaps children more frequently than adults. The 

 cow's udder is occasionally involved in infections 

 with streptococci, which, being excreted in the 

 milk, are capable of causing severe enteritis when 

 the milk is ingested. 



The micro-organism of milk sickness is trans- 

 ferred in a similar way, and only recently it has 

 been shown clearly that man (in Malta) becomes 

 infected with Malta fever by the consumption of 

 the milk of goats. A very large percentage of these 



