34 ON DILATATION OF THE HEART, &C. 
zation of the blood is also proportionably diminished ; it is, 
therefore, easy to conceive two symptoms that must present 
themselves in pneumonia, viz. an oppressed pulse, and venous 
blood, very dark in colour. The left side of the heart having less 
blood to contract upon, less is sent to the extremities, and that 
not having undergone a due change in the lungs; the legs,ears, 
and nose are cold ; from the tumefied state of the lungs, and the 
compressed state of the bronchise and air-cells, the respiration is 
rendered quick, difficult, and laborious; neither of which symptoms 
are present in hydrops pericardii. Again, that obstinate stand¬ 
ing upon the legs until the last in pneumonia, is not observed in 
horses labouring under effusion within the pericardium, parti¬ 
cularly when unaccompanied by much pleuritic affection, as may 
be seen on referring to the case related at page 125 of The Vete¬ 
rinarian for 1833. The symptoms most characteristic of 
hydrops pericardii are—palpitation of the heart; the carotid 
arteries beat forcibly, and are readily recognized on applying the 
finger to their course in the neck; there is a good flow of blood 
through the jugulars, a copious return of blood through the neck 
when the state of the pulse is considered; the surface of the 
body and extremities are warm, and these latter symptoms con¬ 
tinue until within one or two hours of the horse’s death : these 
last mentioned symptoms are also present when the malady is 
accompanied by pleurisy. In a case of this kind, occurring in 
my practice a short time past, the groom, in information to me, 
thus observed, “the horse was as warm all over as a toast when 
he died.” In addition to the above symptoms, there is such an 
expression of anxiety and alarm in the countenance of the 
animal as no other malady produces. I have said the respira¬ 
tion was but little disturbed in hydrops pericardii unattended by 
affection of the lungs, and for this reason, that the lungs are not 
tumefied ; there is no compression of the bronchi® nor air-cells ; 
the blood readily circulates through the pulmonary arteries and 
veins to the left auricle of the heart; the left ventricle is supplied 
with blood to contract upon—blood less thick and viscid, from 
having been oxygenized in the lungs ; consequently the extre¬ 
mities retain their warmth, and the veins their current. When 
the heart is compressed by fluid contained in the pericardium, 
the diastole of the auricles and ventricles is limited; less blood is 
necessarily pumped forward by each contraction; and, in order to 
maintain the circulation, these contractions of the heart’s cavities 
must increase in frequency proportionate with the diminution of 
the volume of blood contracted upon, thus producing that dreadful 
palpitation and throbbing of the organ in the advanced stage of 
the disease. 
