Bauhaus-Universität Weimar

208 
THE PULSE IN DIFFERENT ARTERIES. 
degree of this dilatation of the arteries. His experiment was inge¬ 
nious: he laid bare the common carotid of a living horse for the 
space of three decimeters, or about twelve inches, and passed 
beneath it a tube of white metal, open at one side, which he after¬ 
wards closed by means of a narrower portion, so as to complete the 
tube; he then stopped the ends with wax and fat, and filled the in¬ 
terior of the tube around the artery with water, by means of a glass 
tube which was connected with the metallic tube. At every pulsa¬ 
tion the water rose 70 millimeters* in the glass tube, the diameter of 
which was 3 millimeters, and fell again the same distance during 
each pause. The included portion of artery measured in length 180 
millimeters, and its capacity equalled 11,440 cubic millimeters; and 
since at every beat of the heart it underwent an increase of capacity 
equal to a column of water 3 millimeters in diameter and 70 milli¬ 
meters in height, or about 494 cubic millimeters, it follows that it 
was dilated about ¥V of its capacity. 
The pulse in different arteries.—It was asserted by Bichat, and 
is commonly admitted, that the pulse is synchronous in all the arte¬ 
ries of the body, whatever be their distance from the heart. 
Weitbrecht, Liscovius, and E. H. Webert have shown, however, 
that this is not the case. The pulsation of the arteries near the 
heart is synchronous with the contraction of the ventricle. But at 
a greater distance from the heart the arterial pulse ceases to be per¬ 
fectly synchronous with the heart’s impulse, the interval varying, 
according to Weber, from one-sixth to one-seventh of a second. 
Thus, the pulse of the radial artery even is somewhat later than that 
of the common carotid. The pulse of the facial, at about the same 
distance from the heart, is isochronous with that of the axillary 
artery; while the pulse is felt somewhat later in the metatarsal artery 
on the dorsum of the foot, than in the facial artery and common 
carotid. Weberf has explained the cause of this différence. If the 
blood circulated in perfectly solid tubes, whose walls admitted of no 
extension, the impulse of the blood, driven by the ventricle into the 
arteries, would be communicated even to the end of the column 
of blood, with the same rapidity with which sound is propagated 
through this fluid,—much quicker, namely, than in atmospheric air; 
the pressure of the blood would be transmitted to the finest extremi¬ 
ties of the arteries, with no perceptible loss of time. But, in conse¬ 
quence of the arteries admitting of some extension, particularly in 
length, the impulse given to the blood by the heart distends first 
merely the arteries nearest to the heart. These, by their elasticity, 
again contract, and thus cause the distension of the next portion of 
the arterial system, which also, in its turn, by contracting, forces the 
blood into the next portions, and so on; so that a certain interval of 
time, although a very short one, elapses before this undulation, re¬ 
sulting from the successive compression of the blood, and the dilata¬ 
tion and contraction of the arteries, reaches the most distant parts of 
* A millimeter equals 0'03937 of an English inch. 
■■ In his Treatise De Pulsu non in omnibus Arteriis plane synchronico. 
± Adnotat. Anatom.
        

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