Relative Spread of Particulate and Diffusible Substances in the Skin of Male and Female Rabbits. ∗

In an endeavor to elucidate the physiological basis for the varying inherited, natural resistance to tuberculosis demonstrated in certain inbred rabbit families, 1 it was found that among the factors determining this resistance, the spread of particulate matter in the skin played a prominent role. 2 In general, rabbits belonging to the susceptible families spread intracutaneously injected India ink over a wider area than rabbits belonging to the resistant strains. This observation was considered of significance, for the following reasons. In the resistant families tuberculosis naturally acquired by respiratory contagion, was limited to the lungs, and the rabbits died after a prolonged illness from a strictly localized ulcerative phthisis without spread to the draining lymph nodes and internal organs, a picture resembling in its essential characteristics the reinfection type of adult pulmonary tuberculosis in man. Rabbits of the susceptible families, on the other hand, died of a more rapidly fatal disease, originating in a primary focus in the lungs, soon spreading to the draining tracheobronchial lymph nodes, which became massively enlarged and caseous. Extensive caseous pneumonia without cavity formation developed forthwith and large nodular destructive lesions occurred in many organs from bacilli disseminated by the blood. The disease had the characteristics of a first infection and resembled the childhood type of tuberculosis in man.

There was thus a correspondence between the spread of carbon particles and the spread of tuberculosis in the tissues of these rabbit families.

It is well known that the mortality from tuberculosis is much greater in young women than in young men. In view of the parallel existing between the spread of India ink and resistance to tuberculosis, it seemed of interest to determine if sex differences can be observed experimentally in the spread of particulate matter.