OK ANEURISM OF THE AORTA IK* THE HORSE. 235 
by a white fibrous tunic (the cellular coat), and the interior 
membmne is coriaceous, often covered with fungous irregula¬ 
rities, and even ulcerations. 
These pouches, or distensions of the arterial tunics, generally 
contain a fibrous concretion, either adhering to or detached from 
the aneurismal sac, sometimes of considerable consistence, and 
even disposed in layers. These clots are softer towards the 
place where the sac communicates with the ailerial cavity, and 
sometimes the blood is there unchanged. Aneurisms of this 
kind are principally found on the posterior aorta, and the an¬ 
terior mesenteric. 
It may not be uninteresting to collect what foreign authors 
have said of this disease, 
M. Chouard {Journal Pratique, Sept. 1826) relates two 
cases of aneurism. A mare w^as brought to him with fistulous 
withers. He observed that she could scarcely dmg her hinder 
legs after her. The pulse w^as quick and hard, and the beating 
of the heart could be distinctly heard. As soon as she entered 
the stable she fell on her haunches, and never rose again. She 
was physicked and bled, but on the sixth day she died. 
The internal coat of the aorta was highly inflamed; and im¬ 
mediately behind the renal artery w^as a true circumscribed 
aneurism, as large as a pullet’s egg. A little below was an 
opening in the artery, which prolonged itself in the form of a 
pedicle, and communicated with another tumour, as large as a 
child’s head, filled with fibrous matter, in the form of plates. 
A clot of the same nature, but of less consistence, filled the 
aiteiy posterior to the dilatation. The spinal canal being laid 
open, the membranes which enveloped the spinal chord in the 
lumbar region were highly injected, and the medullary sub¬ 
stance was soft, and without consistence, and surrounded by a 
serous fluid. 
Another mare, usually full of spirit and ready for work, sud¬ 
denly, and without any apparent cause, became dull and in¬ 
capable of exertion. This continued during three or four 
months, when the attention of the veterinary surgeon was di¬ 
rected to the loins. She turned with difficulty; shrunk w^hen 
pressure was made on the lumbar region; was costive; and 
voided her urine and dung with straining and pain. She was 
treated as for nephritis, and became better; but, after a very 
short journey, every distressing symptom returned. 
Two months after this her hinder legs swelled, and several 
ulcers appeared, from which proceeded a considerable serous 
and bloody discharge. The swelling soon subsided, and the 
ulcers healed; but on being led out for gentle exercise, she was 
