PLEUROPNEUMON IA. 
833 
form of prevention,, either with the object of infecting the 
animal with a mild form of disease, or of causing it to incur 
the risk at a time when his life is of little value. Inocu- 
lation with the matter of cattle plague has been extensively 
practised on calves on the Continent. Periodical inoculations 
of lambs with the virus of sheep-pox take place in Saxony. 
Inoculation with the virus of pleuropneumonia originated in 
Belgium, and has been extensively practised for many years 
both on the Continent and in this country. 
By way of preface to the consideration of the subject of 
inoculation with the matter of pleuropneumonia, it must be 
definitely stated as a matter of experience that the disease 
cannot be communicated, as other contagious diseases of 
animals can be communicated by the introduction of a small 
quantity of the fluid obtained from the diseased organs or 
from the system. It is a mere quibble to say that pleuro- 
pneumonia can be induced in the fibrous tissues by inocula- 
tion ; effusion into the meshes of the fibrous tissues can be 
caused by employment of any powerful local irritant, but the 
fair question is, can pleuropneumonia be communicated as 
cattle and sheep-pox can be, by inoculation with a few drops 
of the fluid products of the disease? And the honest answer 
is, Certainly not. Reasoning deductively, therefore, it would 
be fair to conclude that as inoculation with the virus of pleu- 
ropneumonia does not produce the disease either in a mild or 
severe form, it cannot on the general principle afford any pro- 
tection. The originator of the system, however, Dr. Willems, 
adopted the inductive method of inquiry, and he has a right 
to expect that the argument upon the subject shall be con- 
ducted in the same manner and his plan tested by experi- 
ments. In the spring of 1852, Dr. Willems, Professor at the 
Veterinary School at Brussels, addressed a letter to the 
Minister of the Interior, acquainting him with the fact of his 
having discovered a preservative against the lung disease 
which had caused serious losses in Belgium, and describing 
the method of inoculation in these words : — 
“ I take the liquid which exudes from the lung of an 
animal recently slaughtered or dead of the disease ; and I dip 
into it a kind of large lancet, then I make two or three punc- 
tures at the extremity of the tail of the animal which I wish 
to preserve from the malady. A single drop of the fluid suf- 
fices for the inoculation, I have made inoculations with the 
saliva and other fluids, but do not approve of them. I have 
also inoculated in other parts than the end of the tail ; and 
in the course of my observation the inconveniences attending 
the operation on other parts will be alluded to.” 
