282 HEREDITARY DISEASES OF HORSES AND CATTLE. 
and, under some views, it is the portion of the animal frame 
which is especially so endowed. Its first appearance in the 
area vasculosa of the germinal membrane of the embryo is 
prior to the existence of those very organs which, after birth, 
chiefly minister fresh materials to it ; and though undergoing 
constant change, it has this in common with the animal solids , 
and with those equally which are most frequently the subjects of 
hereditary affection .” 
Our next example involves a similar question, and is an 
instance of a disease that can scarcely be conceived in any 
other manner than as circulating in the blood, and conveyed 
to different parts or organs of the body. 
(d.) Rheumatism in Cattle . — There is much that is curious 
in the tendency to rheumatic affections so frequently observed 
in the ligaments and synovial membranes of the joints of 
cattle, and likewise in the fascia or cellular coat of the 
muscles. This disease is attended by stiffness and inability 
to move, pain on pressure, and more or less febrile symptoms. 
Sometimes it attacks one or two joints, and occasionally 
shifts its action to the others. This tendency of the disease 
to shift from one part to another is evidence of constitu- 
tional affection, and dependent on temperament and state of 
the circulating fluids. 
Among the causes which predispose to rheumatism must 
be placed an hereditary tendency and temperament of the 
animal, for, although we find it prevalent in cold, marshy dis- 
tricts, in exposed places, and during the spring and autumn 
months, when there is the greatest vicissitude of heat and 
cold, yet why the same agents* should produce rheumatism 
in one case, bronchitis in another, pleurisy in a third, and 
dysentery in a fourth, and so on, can only be explained by 
supposing that each individual has some particular organ or 
organs which are more prone to disease than other parts of 
its organization. 
(<?.) Chronic Dysentery . — There appears a strong tendency 
* M. Dupuy relates some cases in proof of glanders being hereditary. “ A 
mare,” he says, “ on dissection, exhibited every appearance of glanders : her 
filly, who resembled her in form as well as her vicious propensities, died 
glandered at six years old. A second and a third mare and their foals pre- 
sented the same fatal proof that glanders is hereditary.” 
It must be obvious that all causes, as well as the effects they produce, 
must have an intimate relation to the condition of the living frame, and 
that those which might be quite inefficient on one animal will be more 
powerfully active on another, owing to the state of vital energy at the time. 
The effects produced by various animal and vegetable exhalations on dif- 
ferent horses fully illustrate this position, — producing glanders in some, 
farcy in others, and grease and ophthalmia in very many. 
