Bauhaus-Universität Weimar

Handbook for the Physiological Laboratory. Text
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
alcohol. The proper quantity of water—that is, sufficient to make 
up ten cubic centimeters—is then added, and a straw-coloured, 
nearly limpid liquid is obtained, a single drop of which is a 
sufficient dose. It is injected under the skin of the back with an 
ordinary subcutaneous syringe, and answers best when the effect 
does not manifest itself for some time after the injection. The 
most convenient apparatus for the purpose of exposing the 
mesentery is that shown in fig. 217. The manipulation is fully de¬ 
scribed in Chapter VII. p. 168. It is always desirable to commence 
the examination with a low power. It is then seen that the arteries are 
smaller than the veins, the latter exceeding the former in diameter 
by about a sixth : that the arterial stream is quicker than the 
venous ; that it is accelerated appreciably at each beat of the heart ; 
and that in every artery a space can be distinguished within the 
outline of the vessel, which is entirely free from corpuscles. The 
arterial stream, indeed, is so quick that the forms of the corpuscles 
cannot be discerned, but in the veins both coloured and colourless 
corpuscles can be distinguished ; and it is soon noticeable that, 
while the former are confined to the axial current, the latter show 
a tendency to loiter along the inner surface of the vessel, like 
round pebbles in a shallow but rapid stream. The observation 
may be continued without material change for many hours; but if 
any artery is measured from time to time micrometrically, it will 
be found that after a while it becomes wider. On this dilatation of 
the arteries follows a corresponding though less marked enlarge¬ 
ment of the veins, and, if the attention of the observer is fixed 
upon these last, it is seen that the circulation, which was before so 
active, undergoes a marked and almost sudden slowing. This 
slowing indicates that the membrane, in consequence of its exposure 
to the air, is becoming inflamed ; simultaneously with it, the colour¬ 
less corpuscles, instead of loitering here and there at the edge of 
the axial current, crowd in numbers against the venous walls. In 
this way the vessel becomes lined with a continuous pavement of 
these bodies, which remain almost motionless, notwithstanding that 
the axial current still sweeps by them, though with abated velocity. 
If at this moment the attention is directed to the outer contour of 
the vessel, it is seen that minute, colourless, button-shaped eleva¬ 
tions spring from it, each of which first assumes the form of a 
hemispherical projection, and is eventually converted into a pear- 
shaped body, attached by a stalk to the outer surface of the vein. 
This body, which has thus made its way through the vascular 
membrane, is, I need scarcely say, an amoeboid colourless corpuscle. 
It soon shows itself to be so by throwing out delicate prongs of 
transparent protoplasm from its surface, especially in the direction 
from which it has come. 
The methods to be employed for the study of the circulation


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