Even the most widely divergent of these evolutionary forms can often be made to approach each other and apparently merge into one type. Profiting by the example of Metchnikoff, Nocard enclosed in collodion capsules the bacilli of the human sputum and inserted the capsules into the peritoneal cavity of chickens which had proved refractory to their direct inoculation. This excluded the direct action of the leucocytes from the encapsuled bacilli, but allowed the endosmosis of the serum of the fowl for their nourishment. After a sojourn of four months or more they were transferred to other capsules and again enclosed in the peritoneum and after a second and third transference of this kind it was found that the bacillus had become actively pathogenic for the chicken, having acquired the infecting potencies of the bacillus of avian tuberculosis.
In keeping with the above is the fact that both rabbit and horse are easily infected by the bacillus obtained from birds, and that after a certain number of transmissions through the rabbit the issue of the bacilli of bird and mammal appear to become identical. No less instructive are the cases of the infection of carp by human sputa and the conveyance of tuberculosis to rabbits and Guinea pigs by inoculation with the nodules of the infected carp.
The vitality of bacillus tuberculosis is strong but variable. In sterilized water at 46° to 64° F. the human bacillus survived for fifty to seventy days (Chantemesse and Vidal), the bovine indefinitely (Galtier) and the avian bacillus at a higher temperature one hundred and seventeen days (Straus and DeBarry). In dried expectoration the bacillus of man still infects after nine or ten months (Koch, Schill, Fischer, De Thoma). In infected cow’s lung, dried and pulverized, it infected Guinea pigs at 102 days (Cadeac and Malet). In putrid matter it infected after 43 days (Schill, Fischer), 167 days (Cadeac and Malet), several years in a grave (Schottelius).
It is not destroyed by gastric juice (Fischer, Falk). The bacillus from tubercle of birds has a much greater vitality than that of mammals. Marfucci successfully seeded new media from a culture of two years old, and cultures in artificial media can be started more successfully.
Full sunlight renders sputum on a solid nonabsorbent surface noninfecting in several hours, varying according to the thickness of the layer (Koch, Straus). When sputum is mixed in soil it may survive until the 137th day (Feltz). On woolen cloth it may live five hours (Migneco).
Diffuse daylight, with shading from the sun, killed in seven days (Koch), to eighteen days (Lucibelli).
X-Rays do not arrest the growth of cultures (Blaikie, Pott, Ausset).
A dry temperature of 212° F. for an hour left some of the bacilli still infecting to Guinea pigs (Lartigan).
A moist heat of 140° F. for one hour sterilizes (De Man, Th. Smith, etc.). The scum formed on the milk may still prove infecting (Th. Smith). Half an hour of a moist temperature of 212° F. is sterilizing. Yet in the case of steaks, roasts and boiled meats the size of the piece often prevents the reaching of this temperature throughout, and it becomes unsafe to use any meat in which the redness of the juice shows, that the albumen has not all been fully coagulated (162° F.).
A freezing temperature, −16° to −26° F., does not devitalize the bacilli, even when alternated with thawing at intervals for several weeks (Galtier, Cadeac and Malet).