TYPES OF TUBERCLE BACILLI 93 



showed bovine strains while 352 cases under sixteen showed approxi- 

 mately 25% of bovine infection. Of 592 cases of pulmonary tuberculosis, 

 in children and adults, not a single case could surely be regarded as 

 bovine. 



A subject of great moment is that of the atrium of infection in tuberculosis. 

 While 75% or more of human cases are of the respiratory tract, yet we now have 

 views that Cornet's idea of T. B. containing dust being aspirated, or Fliigge's spray 

 method of infection from droplets of sputum in coughing, may be but rarely operative. 

 The path from intestinal tract to thoracic duct and lungs is direct, so that tuber- 

 culous bronchial glands of lung infection may be by way of intestines. Some 

 European statistics, using von Pirquet's method, have shown 90% of children 

 under fourteen infected while similar American ones have shown about 50%. The 

 prevailing idea is that we get our infection in childhood and show the disease as we 

 approach adult life. Infection after adult life is exceedingly rare, as shown by the 

 rarity of the disease in attendants at institutions for the tuberculous. The 

 respiratory atria would be just as operative for adults as children so the probable 

 explanation is that children in crawling about, where tuberculous material is 

 accessible, may contaminate the fingers and have infection take place by the digestive 

 tract. With bovine infections we are sure that infection of man takes place almost 

 exclusively by the alimentary tract. 



The British Royal Commission in its final report of July, 1911, considered three 

 types of T. B. 



I. The bovine type belonging to the natural tuberculosis of cattle. 

 II. The human type. The type more generally found in man. 



III. The avian type, belonging to natural tuberculosis of fowls. 



The bovine type grows slowly on serum and at the end of two to three weeks 

 shows only a thin grayish uniform growth which is not wrinkled and not pigmented. 

 The human type grows more rapidly and tends to become wrinkled and pigmented. 

 Subcutaneous inoculation of 50 mg. of culture into the neck of calves produced 

 generalized tuberculosis. A similar injection of human T. B. does not cause general- 

 ized tuberculosis but only an encapsulated local lesion. 



Intravenous injection of o.oi to o.i mg. of bovine T. B. into rabbits causes general 

 miliary tuberculosis and death within five weeks. With human T. B. in doses of 

 o.i to i.o mg., similarly injected, the majority of rabbits live for three months. 



Subcutaneous injection of 10 mg. bovine T. B. causes death in 28 to 101 days. 

 Similar injection of human T. B. in doses up to 100 mg. did not kill the rabbits after 

 periods of from 94 to 725 days. The duration of life in injected guinea-pigs is 

 longer with human than with bovine T. B. 



Subcutaneous injections of bovine T. B. into cats produces generalized tubercu- 

 losis while the cat is resistant to human T. B. thus given. 



Recent statistics (Beitzke) show tuberculous lesions in 58% of adults 

 at autopsy Naegli's figures were about 90%. 



It is a question whether the avian type is absolutely distinct; many 

 experiments having indicated the impossibility of infecting fowls with 



