ON THE? CIRCULATION THROUGH IT 183 
veins, you see, remain collapsed, the blood being continually drained out of them 
by the action of gravity; but the arteries, in spite of that action, instead of 
being empty or nearly so, as they were when the limb was previously elevated, 
are distended even to the remotest capillaries. He will now raise the other 
hand, and you observe the extraordinary contrast between the two limbs, both 
in the elevated position, the hand last raised becoming as pallid as the other 
did before the elastic band was applied. 
It is worth while to consider shortly how it is that the constricting bandage 
gives rise to arterial relaxation. It is well known that troublesome after-bleeding 
not unfrequently follows the application of Esmarch’s bloodless method. This 
is commonly attributed to a temporary paralysis of the vaso-motor nerves, in 
consequence of the pressure to which they have been subjected. Now, in the 
experiment which you have just witnessed, one of the two factors in Esmarch’s 
method which might be supposed to have such an effect—viz. the tight elastic 
bandage, applied from the distal extremity upwards, and temporarily com- 
pressing the branches as well as the trunks of the nerves—is absent ; so that 
we have merely to consider the effect of the constricting band upon the nervous 
trunks at the root of the limb. It is no doubt true that in the arm, where the 
soft parts are in small proportion to the cylindrical bone, if, instead of an elastic 
bandage, an india-rubber tube be employed as the constricting agent, in accor- 
dance with Esmarch’s original proposal, the concentrated pressure so exerted 
may, in case of a protracted operation, lead to paralysis of a very troublesome 
if not serious character, both of motion and sensation. But if we follow Esmarch’s 
more recent advice, and diffuse the pressure by using the broad bandage, no such 
effects are observed. I have tried the experiment upon myself, and I have 
found that the bandage, applied sufficiently firmly to arrest all circulation and 
sufficiently long to produce the after-blush in the raised limb, did not affect 
in the slightest degree either the sensation of my hand or the motor power of 
the forearm. And as there is no reason whatever for believing that the vaso- 
motor fibres in the trunks of the nerves are more likely to suffer from com- 
pression of those trunks than the sensory and voluntary motor fibres, the theory 
of paralysis from compression falls to the ground. That which seems to me to 
be probably the true explanation is, that when a part has been deprived for 
a while of circulation, the want of the vital fluid creates in the tissues a demand 
for a supply of it, and that this demand operates upon the vaso-motor nervous 
apparatus of the limb as a stimulus inducing arterial relaxation, in a manner 
perhaps analogous to that in which the ‘ besoin de respirer’, as the French 
have termed it, produces a stimulus to the respiratory nervous system. We 
know that in the case of the arteries different stimuli produce different effects ; 
