32 
Hereditaiy Diseases of Sheep and Pigs. 
deposition of more tubercular matter. These deposits occur in 
almost all the tissues of the body: — in the brain or on its mem- 
branes, causing disturbance of the cerebral functions ; in the 
mesenteric glands, causing derangements of digestion and assi- 
milation ; on the intestinal mucous membrane, frequently 
inducing diarrhoea and dysentery ; and still more commonly in 
the lungs, giving rise to difficulty of breathing, languishing, and 
all the well-known symptoms of pulmonary consumj)tion. 
In all animals the scrofulous constitution is decidedly here- 
ditary, and among sheep we have repeatedly seen it transmitted 
from parent to offspring for three or four generations. The pre- 
cise condition which in such cases is transmitted is unknown. 
It may consist in some alteration in the quality of the blood, or 
the proportion of its constituents, or, more probably, in some 
abnormal state of the soft solids. But in whatsoever this condi- 
tion may consist, it is almost always accompanied by certain 
external appearances, which enable us to distinguish with 
tolerable certainty those sheep in which scrofulous diseases are 
especially apt to develop themselves. They have thin, small 
necks, narrow chests, pot bellies, thin and delicate skins, fine 
wool sparingly spread over the head, legs, and belly, tender eyes, 
weak circulation, small bones, soft flabby muscles, and a general 
disproportion among the different parts of the body. An animal 
of such a conformation, when exposed to any health-depressing 
influences, will certainly become affected by scrofula in one or 
other of its various forms. Neither management nor medicine 
can purify it of its inherent and ever-present tendency to disease. 
It must not, however, be supposed that scrofula invariably 
results from hereditary predisposition, for it may be induced 
even in the most healthy and vigorous stock by impure air, in- 
sufficient nutriment, and exposure to wet and cold. Thus many 
of the beasts and birds in our Zoological Gardens fall victims to 
scrofulous disease from being brought from a warm to a cold 
climate, or perhaps rather on account of the close atmosphere 
and artificial condition in which they are kept. Rabbits shut 
up in cold, damp, dark, and narrow boxes, and fed on food not 
suited to t!iem, soon die of tubercular disease.* All influences 
inimical to health, and tending to repress the elimination of 
effete and poisonous matters from the body, are capable of 
inducing a strumous constitution, and always greatly aggravate 
any inherent tendency to it. Scrofulous disease, when thus 
produced by external circumstances, is always more manageable, 
and more capable of cure, than when hereditary ; but in whatever 
manner pi'oduced, it is, like other constitutional diseases, accom- 
* Watson's Principles and Practice of Physic. Third Edition, vol. i., p. 205. 
