OF THE BLOOD. 
353 
power, the force of that organ has never been ascertained. It is 
estimated by some at . a few ounces only, and by others at 
nearly two hundred thousand pounds. Supposing, however, 
according to the statement of some physiologists, that the blood 
be propelled into the aorta at each contmction of the left ventricle 
with a velocity of 120 feet in a minute, that velocity will soon 
diminish with the calibre of the vessel and the tortuousness of its 
course, and will not be the same in any two portions of the frame. 
The enquiries of other philosophers have not led to a more de¬ 
finite result. They have calculated the quantity of blood con¬ 
tained in the vessels, and the quantity which the ventricles of 
the heart will contain; then, dividing the general mass by the 
contents of ventricles, they have the number of pulsations in 
which a complete circulation of the fluid takes place. There are, 
however, some unfortunate and insurmountable difficulties attend¬ 
ing this computation. The number of pulsations in a given time 
differs widely in different species of animals, and in different 
animals of the same species; and the capacity of the ventricles 
differs yet more. It is well known to every veterinarian that the 
left ventricle is, in some full-grown horses, twice as capacious as 
in others. In the right ventricle this vaiiation is yet more re¬ 
markable. As, therefore, the actual quantity of blood cannot be 
ascertained, nor the capacity of the ventricles scarcely guessed 
at, a calculation of the pulsations will afford a very imperfect 
estimate of the rapidity of the circulation. 
M. Hering has adopted a much more satisfactory method of 
experimenting. He sought out some substance readily soluble, 
easily detected in the minutest proportion by certain chemical 
tests, and which, mingling with the blood, would not materially 
affect the circulation. He fixed on the hydrocyanate of potassium. 
He dissolved one drachm of it in eleven drachms of water, and 
he found that he could detect it in the serum in the proportion of 
one part in 20,000, by means of the sulphate of iron. He opened 
the jugular, and introduced two or three ounces of the solution 
into the vein. He did not inject it, because he would not add to 
the force of the circulation, but poured it into a funnel, and thus 
suffered it to mingle with the blood. He then, at short intervals, 
drew blood from various parts of the body; and when the serum 
was separated, exposed it to the action of a solution of the sul¬ 
phate of iron. If a blue precipitate was foimed, it indicated the 
presence of the hydrocyanate -of potassium. The results will 
interest the readers of the Veterinarian, and surprise many of our 
physiologists. 
In from twenty to thirty seconds the hydrocyanate passed 
from one jugular to the other; it reached the submaxillary 
2 T 
