Pleuro-Pneumonia of Cattle. 163 



I am also deeply grateful to the trustees of the Walter and 

 Eliza Hall Research Fund, for the appointment as "Walter and 

 Eliza Hall Research Fellow in Veterinary Science," and for pro- 

 viding from their fund the moneys required to cover the ex- 

 penses incidental to this research work. 



Historical Resume. 



The earliest conception of the etiology of pleuro-pneumonia 

 was that cold was the primary cause operating in the produc- 

 .tion of the disease. 



in 1852 Willems (20) 2 as a result of a number of observa- 

 tions and experiments, demonstrated that the disease was con- 

 tagious, and that- healthy animals had to come into close con- 

 tact with diseased animals before the disease would spread from 

 one to the other. He further demonstrated that, in order that 

 the disease could spread, it was necessary for contact to be be- 

 tween living animals. The disease was not spread when healthy 

 ..animals were exposed to contact with the carcase of an animal 

 which had died from contagious pleuro-pneumonia. His experi- 

 ments with pleuritic serosity are of special interest, as they mark 

 the commencement of a system of immunisation against the 

 disease, which system, with but very slight modifications, is ex- 

 tensively practised at the present day. Willems found that if a 

 .small quantity of pleuritic serosity, taken from an animal af- 

 fected with pleuro-pneumonia, was injected subcutaneously be- 

 hind the shoulder of a healthy animal, there followed, after an 

 incubation period varying from 8 to 15 days, a firm swelling, 

 later becoming fluctuating, hot and painful, which then rapidly 

 increased in size, and gave rise to an invading oedema of the 

 whole of the connective tissue in the region of the inoculation. 

 This swelling contained a large quantity of clear amber-coloured 

 serosity, a small quantity of which injected into another healthy 

 bovine animal behind the shoulder gave rise to a similar swelling 

 at and around the site of inoculation. Death of the experimental 

 animals almost invariably followed these experimental inocula- 

 tions behind the shoulder, but when inoculations with the same 

 materials were made subcutaneously in the tail, a few centimetres 

 from the tip, there followed a mild reaction, with some swelling 

 of the tail, which usually subsided in the course of 15 to 21 days, 

 but which occasionally terminated in a more or less extensive 



2. Reference is made by numbers to " Liter ature Cited," pp. 63-65. 



V2A 



