34 CONTRIBUTIONS TO ZOOLOGICAL PATHOLOGY. 
Attention, however, needs only to he directed to the subject, and 
there can be little doubt that its high importance in practice, and 
the many interesting facts that are connected with it, will speedily 
cause it to form an object of interest. 
Aneurisms are admitted to be of two kinds in their pathological 
conditions, — true and false. True aneurism consisting of a morbid 
change in one or other of the coats of the vessel, followed by a 
general dilatation of these, of a partial dilatation, or of solution of 
continuity in some of its tunics, with distention of the others, and 
with or without the deposition of fibrine within this dilatation ; 
and false aneurism, where a solution of continuity occurs in the 
structures of all the coats of the vessel, followed by an extravasa- 
tion of its blood into the surrounding tissues. Such are the usual 
conditions that exist in the human individual ; but in the horse, 
independent of the simple, true, or false, aneurism existing, there 
also occurs in the tumours the presence, in the majority of cases, 
of hematoic entozoa or worms , which modify the nature, course, 
and termination of these pathological changes in a ver}' important 
degree. It is to the latter form of disease that the present remarks 
refer, and to which the term worm-aneurism has been applied by 
Rayer, an accurate account of which will be found in his paper, 
Recherclies Critiques et Nouvelles Observations sur V Aneurysme 
Vermineux , in the Archives de Med. Comparee, No. 1, 1842. 
An interesting example of this worm-aneurism came under my 
notice a short time ago, attended with fatal consequences. 
In August 1845, a friend purchased a very handsome bay horse, 
for a hunter, seven years off, and fifteen hands high. He had been 
in the possession of his former owner ever since he left his breeder’s 
hands at the age of four years, and during this period he had been 
regularly hunted every season to a moderate extent, and never had 
been off work for any time in consequence of disease. When re- 
cently sold, he appeared to be in excellent condition ; was parted 
with “ for no fault,” and the usual certificate of warranty was 
given. On coming into the possession of the last purchaser, the 
work into which he was put scarcely exceeded that of simple exer- 
cise ; but one day, after a gentle gallop, he was found to be much 
more done up and exhausted than usual, and on being brought to 
the stable he could scarcely stand upon his limbs, which tottered 
under him : he was restless, and staggered from side to side ; there 
was heaving in his flanks; his coat was bedewed with perspira- 
tion ; and he hung upon his halter, until in a short time he dropped 
on his quarters, and gradually sunk before professional aid could 
be obtained. 
Ten hours after death the carcass was opened, and this was 
found to have resulted from the bursting of an aneurismal tumour 
