336 PROTECTIVE INOCULATIONS. 
spiratory passages. Subcutaneous injections cause a painful local 
tumefaction, often followed by an abscess, but without the general 
symptoms of influenza. 
Experiments have been made in’ Germany by Hell, Siedamgrotzki, 
and others, which indicate that the subcutaneous injection of blood 
serum from immune horses may confer immunity on other horses. 
Hell usually injected forty cubic centimetres at a time, and repeated 
this at intervals until two hundred to two hundred and forty cubic 
centimetres had been injected in the course of two or three weeks. 
He also reports the results of treatment by injections of blood serum 
into the trachea in horses already infected, and thinks these injections 
had a favorable influence on the course of the disease. Experiments 
made subsequently by Toepper have givena similar result, but others 
have not been so fortunate, and the immunizing value of blood-serum 
injections, as practised by the authors referred to, seems to be still a 
matter of some doubt. Toepper (1893) gives full directions for col- 
lecting the serum and a detailed account of results of experimental 
inoculations made by himself and others. He prefers to inject the 
serum into the breast over the ensiform cartilage. No reaction oc- 
curs after the injection. 
PLEURO-PNEUMONIA OF CATTLE. 
Protective inoculations against this disease have long been success- 
fully practised. For this purpose serum obtained from the lungs of 
an animal recently dead has been employed, this having been proved 
by experiment to be infectious material, although the exact nature of 
the infectious agent present in it was not determined. 
Willems, who was one of the first to advocate the use of protective 
inoculations in pleuro-pneumonia (1852), gave a lecture in 1894 in 
which he reviewed the evidence in favor of these inoculations in 
the disease under consideration. Various methods had been em- 
ployed. Thus Willems states that the natives of the banks of the 
Zambéze cause animals to swallow a certain quantity of the liquid 
from the pleural cavity of an animal recently dead, and thus give 
them immunity. The virus has been injected into the circulation by 
some experimenters, and others have proposed to attenuate it by heat. 
But the method which has been most extensively employed is that 
discovered by the Dutch settlers at the Cape of Good Hope (the 
Boers), and consists in inoculating animals in the tail with serum 
from the lungs of an animal recently dead; or with a virus obtained 
from the tumefaction produced by such an inoculation in the tail. 
