ON DILATATION OF THE HEART, &C. 33 
paratively of unfrequent occurrence. In the case of the black 
mare, given page 80 of The Veterinarian for 1833, the left 
ventricle was much dilated ; but its corresponding auricle was 
unchanged, nor had the lungs in the least participated in the 
general derangement of the system : the fatal influence of this 
state of the left ventricle does not appear of that serious con¬ 
sequence to the circulation as is that condition of the right. 
Hydrops Pericardii . 
. Thi s is of more frequent occurrence than either hypertrophy 
or dilatation. It most frequently accompanies pleurisy : indeed, 
it is inflammation of a contiguous serous membrane; and 
but few horses die of acute pleurisy that do not present, on 
post-mortem examination, more or less sero-sanguineous fluid 
within the cavity of the pericardium. It is also by no means un¬ 
frequent, that pleuritic horses are cut off by hydrops pericardii, 
in which inflammation in the pleura had considerably diminished, 
and that in all probability would have recovered, but for the effu¬ 
sion into the pericardium. But, besides this acute pericarditis, the 
heart is subject to a subacute inflammation of the serous mem¬ 
brane covering and investing it, by which a whey-coloured fluid 
is effused into the pericardial sac: the symptoms gradually but 
more slowly develop themselves than in the acute case. One of 
our best veterinary writers observes, when speaking of the 
diseases of the horse’s heart, “ that the subjects of hydrops 
pericardii manifest no signs that lead us to the seat of their 
malady, the disease being generally mistaken for pneumonia.” 
But the symptoms of hydrops pericardii are well marked, as I 
shall be able to shew, in those cases unaccompanied by pneu¬ 
monia, and also in cases where the lungs are but slightly 
inflamed. In cases of pleurisy, where inflammation commences 
at the same time in the pericardium, or, in other words, when 
pericarditis exists with pleurisy (and it is of pleurisy, and not 
pneumonia, that pericarditis is a frequent accompaniment), we 
shall have sufficient signs to guide us in our prognosis, and for 
reasons stated at the commencement of these papers, it is well 
for us to be able to decide on its existence; for whenever much 
water is collected in the pericardium, the case is sure to be fatal, 
as I know not of any mechanical means within our aid by which 
the fluid can possibly be extracted, and remedial measures are of 
no avail. 
In inflammation of the substance of the lungs (pneumonia) 
the flow of blood through them is obstructed in degree with the 
extent of the inflammation existent in that viscus ; the arteriali- 
VOL. VII. E 
