Tuberculosis. 457 



'disease lasting for years with little or no appreciable advancement, 

 and not a few subjects appear to make a permanent recovery. 



On every hand this evolutionary tendency of the bacillus tuber- 

 culosis places itself in evidence, demanding a recognition of the 

 fact, that more or less transient or lasting variations in accordance 

 with previous or existing environment, control to a large extent 

 the transmissibility of the disease among different genera and 

 ■even among individuals of the same genera and species, and also 

 the fatal progress, or the mild and evanescent issue of the infection. 



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 en- 

 -closed 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 extended 

 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 in- 

 definitely (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 



