Abstract
The pioneer studies of Lewis and Wright 1 on inheritance factors in tuberculosis in guinea pigs as well as the writer's observations 2 have prompted a continuance of their studies.
By brother and sister inbreeding of rabbit groups for 4 to 5 generations families have been developed which exhibit varying, inherited, specific resistance to tuberculosis. This has been determined by exposing the succeeding generations of the different families to artificially infected rabbits in specially constructed large cages separated in the middle by a fine wire mesh screen. On one side of the screen are placed rabbits artificially infected with virulent bovine tubercle bacilli. The bacilli shed by these rabbits, chiefly in their urine, are inhaled by representatives of the different rabbit families which are placed simultaneously on the opposite side of the screen. At stated intervals the contacts are tested with tuberculin. Since by this method the disease acquired by the contacts is nearly always of pulmonary origin, their lungs are X-rayed at the same time. The onset and progress of the disease are thus determined.
It was found, after excluding′ all known environmental factors that the genetic constitution of the rabbit per se may determine the type of disease developed on first natural contact with the tubercle bacillus. Those hereditarily most susceptible develop a disease of short duration analogous to infantile tuberculosis. A primary focus develops in the lung, which is accompanied by massive caseation of the draining tracheobronchial lymph nodes. Soon this primary focus undergoes softening and the released bacilli invade the blood stream, so that the animal dies shortly of generalized miliary tuberculosis (Fig. 1). The animals of somewhat greater resistance develop a disease of longer duration analogous to the so-called childhood type with caseous pneumonia, massive involvement of the tracheobronchial nodes and large destructive nodular lesions of hematogenous origin in different parts of the body such as the kidneys, eyes, bones, etc. (Fig. 2).
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