682 WEST OF SCOTLAND VETERINARY MEDICAL ASSOCIATION. 
M. Billard (Addison, p. 197), “The ovum must be influenced by 
the condition of the mother, children having been born healthy, 
sick, and convalescent, or recovered from former disease.” 
Is Tubercle Infectious or Contagious ?—I have seen, Mr. 
President and Gentlemen, many circumstances in the human 
subject, painful circumstances, too, that have biassed me strongly 
to the side of those who believe in the infectious nature of 
tubercle, at any rate, at certain distances, and provided always 
that the system of the exposed individual is in such a peculiar 
condition as to pre-dispose it to the influence of the infection. 
On the other side, I have seen a cow remain in a stock for 
months and years, known to be the subject of phthisis, without 
any other animal becoming affected, either at the time, or sub¬ 
sequently. 
As to contagion: it has one thing necessary to establish the 
contagious character of a disease, viz., the fact of its being 
capable of propagation by inoculation. Some remarkable and 
decisive facts have come under the notice of my colleague, Pro¬ 
fessor Williams, as to both the infectious and contagious 
character of tubercle amongst birds, and these facts I have no 
doubt he will be happy to relate himself. 
If the contagious character of tubercle is established, another 
(though perhaps a remote one) source of contamination is opened 
up before us, viz., from persons or animals eating raw or impro¬ 
perly cooked meat, or more strongly, livers or other internal 
organs, from animals that have suffered from this affection. 
Predisposing or Exciting Causes .—These are of as much im¬ 
portance to us, and as well worthy of consideration, as any part 
of this subject, inasmuch as in a proper knowledge of these is fore¬ 
shadowed, the means to be had recourse to in prevention. Pirst 
and foremost, then, we must place an hereditary predisposition 
or conformation, especially if intensified by increased or multiplied 
consanguinity; hence we find that narrow-chested, light-barrelled 
animals are very susceptible to tubercle, and this conformation is 
always transmitted from parent to progeny, and becomes 
strengthened by each transmission, thus accounting for its 
appearance in herds where breeding in-and-in has been carried on 
to a great extent; light coloured animals are also supposed to 
be more susceptible, though my experience does not bear this 
idea out; debility, arising from any cause (and this is the great 
cause of tubercle with some authorities); a general constitutional 
weakness (which may or may not be hereditary) will most cer¬ 
tainly render an animal more amenable to the exciting causes of 
the disease; but how many people, as well as animals (of sound, 
untainted constitutions), are subjected to hunger, exposure, 
noxious exhalations, variable temperature, fatigue, and disease, 
