32 CITY MILK SUPPLY 



If only 1 per cent, of these in this country were due to bovine infection 

 it would mean a loss of 1,600 lives a year but the percentage is believed 

 to be considerably greater, being placed at 7 per cent, by some. It is 

 recognized that in all probability practically none of the pulmonary 

 tuberculosis is due to bovine bacteria and that were all bovine tubercu- 

 losis stamped out, the tuberculosis problem would be simplified but not 

 greatly reduced in magnitude. Japan and other countries, that are not 

 consumers of milk and dairy products, have a great deal of tuberculosis. 

 On the other hand, it is becoming patently evident that tuberculosis of 

 bovine origin is largely responsible for surgical and abdominal tubercu- 

 losis, especially among children. Furthermore, it is to be remembered 

 that practically all bovine bacteria isolated from infections in man 

 were acquired from the ingestion of dairy products. 



Nature of Tuberculosis. Tuberculosis like other diseases has three 

 well-marked stages, the prodromal or incubating period, the period of 

 sickness, and the period of recuperation or recovery. It differs from many 

 other infectious diseases in that all of these periods may be prolonged. 

 It is likely to be slow and insidious in sharp contrast to such diseases as 

 smallpox and measles which commonly develop within 2 weeks after 

 exposure and are soon over. In some diseases like diphtheria and tetanus, 

 the causative germs elaborate poisons called toxins that cause the 

 death of the patient unless they are neutralized in some manner, but in 

 tuberculosis the germs do not kill in this way. They imbed themselves 

 in the tissues of an organ and by their growth injure it, of ten eventually 

 destroying it and so, if the organ is a vital one, cause death. Often the 

 first warning given by the disease is the impairment of the function of 

 some organ which makes the victim feel sick. 



After the germs have secured lodgment they grow and produce the 

 excrescences called tubercles which are so characteristic that they have 

 given the name tuberculosis to the disease. The tubercles are soft and 

 cheesy or hard and calcified; they may remain isolated or may be con- 

 fluent and form a mass of corruption. In several ways the body tries 

 to rid itself of the invading organisms. One defense is to surround the 

 diseased spot with a thick wall of fibrous tissue thereby isolating it and 

 arresting its development. Where this is successful the progress of the 

 disease is stopped, and it may stay arrested for years during which time 

 the animal may be a useful creature, but often the attempt to form a wall 

 is abortive or only temporarily successful, the germs breaking through 

 the defense and spreading the disease. Sometimes the only organ 

 involved is that first attacked, in which case the disease is said to be local- 

 ized but often it spreads to other organs and sets up a generalized infec- 

 tion. Sometimes the tubercles are scattered widely in the form of little 

 hard bodies like millet seeds and give the form of the disease known as 



