PLEURO-PNEUMONIA. 
549 
mentalist in this country ? I do not undervalue experimenta¬ 
tion. On the contrary I would give it every support in my 
power; but at the same time I do not anticipate that substan¬ 
tial good can come out of it. In this country experimenta¬ 
tion by veterinary surgeons, whether associated with biolo¬ 
gists or not, has never been liberally encouraged, and even 
when attempts have been made by some of us to improve the 
method of inoculation, those attempts have been met with 
undeserved and ignorant censure, even from amongst the 
ranks of our own profession. 
The Great Cause of its Persistence. 
If the stamping out process has not taught us much, it has 
at least gone far towards verifying the opinions we have held 
as to the nature of the disease and the causes of its persist¬ 
ence amongst us. It has emphasized my contention of many 
years’ standing, that the great cause of the persistence of 
pleuro-pneumonia in this country is the existence of infective 
centers of the disease in the lungs of animals which have been 
exposed to the contagion, but in whom there has been little 
or no evidence that they are the subjects of the malady. It 
is now some fifteen or sixteen years since I first promulgated 
the belief I had arrived at as the result of observation and 
experience, that animals which had suffered from the disease 
were 
Living Centers of the Infection, 
and that they were a source of untold mischief. This belief 
or opinion was, on its publication, endorsed, in the first place, 
by Professor Ferrein of Berlin, and it has been accepted in 
this country by all veterinary surgeons whose opinions are 
worth notice or respect; and the result of the Slaughter Order 
has more than established the truth of my belief, for with few 
exceptions the outbreaks that have taken place in this city 
during the last eighteen months have been traceable to such 
centers of infection, and particularly has this been the case 
in those outbreaks which owed their origin to cows from 
Cumberland, These infective centres have been a source pf 
