The tubercle bacillus undergoes no proliferation outside the body and its occurrence in nature depends on the distribution of the infected excretions, particularly the sputum, of man. Hence it is found most abundantly in the rooms and homes of patients and in tuberculous wards of hospitals. Reception of sputum on the handkerchief of the patient, where it subsequently dries, and its discharge on the floor in public places, where it quickly becomes pulverized, as in street cars, are conditions which favor dissemination and the infection of others. In unconfined places which are exposed to the action of light and sun, as the streets and sidewalks, the danger is less on account of the shorter life of the organism under these conditions and the greater volume of surrounding air. The calculation of Heller that a tuberculous patient may excrete 7,200,000,000 of bacilli in a lay suggests the
IMMUNITY.. JAMA. 1905;XLV(15):1083–1085. doi:10.1001/jama.1905.52510150047003
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