PARASITIC BACTERIA. 133 



even after it is swallowed and has passed into 

 the stomach or intestines. This appears particu- 

 larly true of milk bacteria. Under these condi- 

 tions the bacteria are not in any proper sense 

 parasitic, since they are simply living in and 

 feeding upon the same food which they consume 

 outside the body, and are not feeding upon the 

 tissues of man. The poisons which they produce 

 will continue to be developed as long as the bac- 

 teria continue to grow, whether in a milk pail or 

 a human stomach. If now the poisons are ab- 

 sorbed by the body, they may produce a mild or 

 severe disease which will be more or less lasting, 

 continuing perhaps as long as the same food and 

 the same bacteria are supplied to the individual. 

 The most important disease of this class appears 

 to be the dreaded cholera infantum, so common 

 among infants who feed upon cow's milk in warm 

 weather. It is easy to understand the nature of 

 this disease when we remember the great number 

 of bacteria in milk, especially in hot weather, 

 and when we remember that the delicate organ- 

 ism of the infant will be thrown at once into 

 disorder by slight amounts of poison which would 

 have no appreciable effect upon the stronger 

 adult. We can easily understand, further, how 

 the disease readily yields to treatment if care 

 is taken to sterilize the milk given to the pa- 

 tient. 



We do not know to-day the extent of the 

 troubles which are produced by bacteria of this 

 sort. They will, of course, be chiefly connected 

 with our food products, and commonly, though 

 not always, will affect the digestive functions. It 

 is probable that many of the cases of summer 

 diarrhoea are produced by some such cause, and 



