164 G. G. Heslop: 



necrosis of a portion of the tail. These benign reactions, he an- 

 nounced, were productive of a marked degree of immunity against 

 natural infection with the disease At no time, as a result of these 

 inoculations, either behind the shoulder, or in the tail, was he 

 able to demonstrate that they gave rise to a definite pleuro- 

 pneumonia of the lungs, similar to that seen in animals naturally 

 infected. He noticed, however, that the swelling produced as a 

 result of the subcutaneous injection of lymph behind the shoulder 

 had many features histologically comparable with the condition 

 set up in the lungs by natural infection. 



In 1883 Pasteur (16) carried out some experiments with the 

 so-called "lymph" (pulmonary and pleuritic exudate), and he 

 declared that the lymph contained pure virus, which could not 

 be cultivated on ordinary media. 



"Sussdorf (1879), Bruylants and Verriest (1880), Putz 

 (1881), Himmelstoss (1884), Lustig (1885), Pods 'and Nolen 

 (1886), isolated and described various microbes without estab- 

 lishing their specificity." (12) 3 



In 1895 Arloing (1) isolated from cases of pleuro-pneumonia 

 a short non-motile bacillus, which he named the pneumo-bacillus- 

 liquefaciens-bovis, and which he claimed was the causal organ- 

 ism of pleuro-pneumonia. Pure cultures of this organism, ac- 

 cording to Arloing, when introduced intra-pulmonarily into 

 healthy animals, were capable of producing the characteristic lung 

 changes seen in naturally infected cases of pleuro-pneumonia, 

 while subcutaneous injection of pure culture into susceptible ani- 

 mals produced immunity. Arloing's experiments are open to a 

 considerable amount of criticism, owing to the technique he em- 

 ployed, and although his experiments were repeated by others,. 

 his announced results could not be confirmed. 



In 1898 Nocard and Roux (13), by means of an ingenious ex- 

 periment, succeeded in artificially cultivating the virus of pleuro- 

 pneumonia in bouillon contained in collodion sacs, which were 

 inoculated with a trace of pulmonary serosity from an animal 

 affected with pleuro-pneumonia, and were then embedded in the 

 peritoneal cavities of rabbits. After 15 to 20 days the bouillon, 

 which at the commencement of the experiment was perfectly 

 limpid, showed a faint opalescence, and thereafter the rabbits be- 

 came emaciated. The contents of control sacs similarly treated, 

 but not inoculated with serosity remained perfectly clear and 



3. P. 449. 



