SECT. XI. PHYSIOLOGY. 103 
texture, according to the nature of its structure ; 
and the veins being more expansive than the 
arteries, are consequently more readily affected by 
variations of the vital force. 
ecxiin. In neuralgia there is a diminution of 
arterial as well as venal expansibility, but the 
delicate veins of the sciatic neurilema being most 
easily affected, they collapse, and are unable ‘to 
absorb the: blood from their capillaries, which 
become distended, causing intolerable pain of the 
sciatic nerve. I have never known this pain ex- 
tend. to the divisions of the sciatic nerve beyond 
the ankle, where the points of contact between the 
blood-vessels and divisions of this nerve become 
multiplied. 
cexLiv. The distention of the capillaries with 
blood not being from increased arterial action, 
detraction of blood seldom gives even temporary 
relief; the small veins of the neurilema remain 
obstinately contracted, and depletion may ‘be 
earried to any length, without equalizing the 
circulation. 
ccxLv. When the expansibility of the veins 
of the sciatic neurilema is renewed, by restoring 
the action of the nerve with the nitrate of silver, 
the disease is removed, by absorption, in a few 
days. But if the application of the lunar caustic 
be so great as to affect the expansibility of both 
the arteries and veins, the pain'is more severe for 
