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MESSRS. W. H. HOWELL AND F. DONALDSON 
were favourable, the oedema of the lungs not occurring to any marked extent until 
after many observations had been made. 
In speaking briefly of former attempts to compute the amount of blood thrown 
out from the left ventricle at each systole, it is hardly necessary to refer to the 
earlier observations made upon dead hearts, since these are universally allowed to be 
of but little value. We need only say a few words about the later experiments upon 
living animals made by Volkmann, Vjerordt, and Fick. 
The method used by Volkmann (1) is too well known to require any extended 
description. It is based upon the principle that the velocity of the blood stream is 
inversely as the width of the channel in which it flows. The line of argument used is 
this—starting from the aorta at its origin, which he calls the first vascular section, 
we have, first, a division into the innominate and the aorta beyond the innominate ; 
this he calls the second vascular section, and supposes that the velocity of the stream 
in each of the two divisions of this section is the same, and is as much less than the 
velocity in the undivided aorta as their united sectional areas are greater than the 
sectional area of the aorta. The innominate in turn divides into branches making 
a third vascular section ; the velocity in each of these branches is again the same, and 
as much less than the velocity in the innominate as the sum of their sectional areas 
is greater than the sectional area of the innominate. Then by determining the 
velocity of the blood in one of these last divisions by means of his hamodromometer, 
and measuring the width of the different vascular sections mentioned, the necessary 
data were obtained for estimating the quantity of blood passing through the sectional 
area of the ascending limb of the aortic arch in a given time, and therefore, knowing 
the pulse-rate, the quantity of blood sent out from the ventricle at each systole. 
The whole method is evidently subject to many serious errors, the most important 
of which is that the velocity of the blood stream, as has been shown by Dogiel, 
undergoes such great variations that but little positive value can be attached to an 
experimental determination of it at any one time, or even to the mean deduced from 
many observations. 
Besides this, the method employed to determine the width of the vascular sections 
is open to objection. The means used for determining this factor were briefly these. 
After obtaining the velocity in the carotid, the diameter of that vessel was measured ; 
the animal then killed, and the vascular system injected from the abdominal aorta 
with melted wax, and under such a pressure that the carotid assumed the same 
diameter as that which it had previously wdien the velocity in it was measured. 
After the wax had hardened the diameter of the aorta and of the other vessels was 
obtained. As Volkmann himself says, one is not at all sure in this case that 
the parts of the vascular system under consideration will be distended in the same 
proportion to each other that existed during life; he thinks, however, that this 
will make no difference as long as the carotid possesses the same diameter that it 
had when the velocity in it was measured, since any over-valuation of the width of 
