62 The Nerves of Capillary Vessels and their 
tissues and organs of man and the higher animals is constantly 
regulated and controlled. By the contraction of the muscular 
fibres of the small veins the lateral pressure of the blood upon the 
capillary walls may be altered from time to time, and the rapidity 
with which the blood traverses the capillaries caused to vary. 
The smallest veins, like the capillaries, are destitute of muscular 
walls, but are remarkable for the great number of oval bioplasts 
connected with their coats and projecting into the interior of the 
vessel. In many of the smaller veins the united area of the bio- 
plasts would considerably exceed that of the membranous portion of 
the wall of the vein. These bioplasts are the agents concerned in 
the absorption of nutrient constituents from the blood and their dis- 
tribution in an altered form to the tissues. It is these bodies which, 
by removing and taking up certain of the substances dissolved in it, 
promote the onward flow of the blood. Thus the vis-d-fronte 
action, which has been so frequently referred to, may be accounted 
for and explained. 
Action of the Nerve Fibres of the Capillary Vessels in Inflam- 
mation. ' 
It is not possible that nerve fibres lying so very close to the 
capillary walls should be uninfluenced when the volume of blood in 
the capillary is increased, as in congestion. By the long-continued 
stretching or pressure to which these delicate nerve fibres would be 
subjected, partial paralysis would be induced. 
In inflammations and in the long-continued feverish condition, 
the growth of bioplasm external to the vessels and resulting from 
the multiplication of bioplasts which had passed through the capil- 
lary walls in the stage of congestion, must seriously impair the 
action of these nerve fibres ; and there is good reason to think that 
some of the phenomena that ensue are the direct consequence of 
the nerve disturbance. Let us therefore consider very briefly the 
changes occurring in one of the slightest and most familiar forms 
of inflammation — a common flea-bite. 
The tissues which are perforated by the cutting instrument of 
the flea as it penetrates, would be, first, the epithelium ; next, that 
modified connective tissue with its “ corpuscles ” (masses of bioplasm) 
of which the papillae and the most superficial layer of the true skin 
consist. Embedded in this connective tissue are certain vessels and 
nerves. The following tissues would be more or less damaged by 
the passage of any sharp instrument through the different layers of 
the skin, — cuticle, connective tissue, the capillary vessels (lymphatics 
in some instances), and nerves; and these are the only tissues which 
can be affected under the circumstances alluded to. Now the 
capillaries, as we know, receive blood from the arteries ; and the 
