832 
PLEUROPNEUMONIA. 
nective tissue of the lung, and also in the same structure of 
the tail, after inoculation, consists of an albuminous fluid con- 
taining blood discs and large exudation corpuscles. Dr. 
Willems refers to minute moving bodies, which he detected 
in the fluid that was pressed from diseased lungs ; these 
bodies, and others — Bacteria and Vibriones — have been con- 
stantly met with, but they are not peculiar to the exudation 
matter of pleuropneumonia. 
The blood, immediately on being drawn from the vessels, 
presents the phenomenon of stellate red particles. These 
however, are often found in healthy blood, and are common 
in various diseases. 
In the milk obtained from diseased animals, large granular 
corpuscles, identical with those which have been observed in 
cattle plague and foot-and-mouth disease, are always found ; 
and in the muscular tissue, the peculiar bodies known as 
psorosperms are frequently very abundant. These bodies 
have also been detected in large numbers in the flesh of cattle 
affected with cattle plague, malignant catarrhal fever, and 
foot-and-mouth disease. In many instances perfectly healthy 
subjects have been found to be infested with them, although 
not to so great an extent. 
Preventive Measures : Inoculation , Isolation } and 
Disinfection. 
Contagious and infectious diseases only occur once as a 
rule in the life of the individual. Exceptional cases have 
been quoted often enough, their occurrence is admitted, but 
they do not happen so frequently as to seriously affect the 
practical bearings of the rule. An animal which has re- 
covered from cattle plague, pleuropneumonia, sheep-pox, or 
foot-and-mouth disease is for all practical purposes protected 
against the disease for the future, and the protection appears 
to be equally certain whether the attack has been a mild or 
severe one. Acting on a knowledge of this fact, investiga- 
tors have had recourse to experiments both on men and the 
lower animals, in order to ascertain what are the easiest 
and most certain means of artificially producing the disease 
in a mild form under favorable circumstances as a protection 
against a natural attack, which is most likely to happen when 
all the circumstances are opposed to its favorable progress. 
Inoculation with minute quantities of the virus of contagious 
and malignant diseases was early practised both on the 
human subject and also on the lower animals ; in all coun- 
tries veterinary authorities have tested the efficacy of this 
