148 ON THE STATE OF THE BLOOD AND 
human body, is applied to the elucidation of the state of the 
blood and of the bloodvessels in an inflamed part in man. 
The First Chapter treats of the bloodvessels of the web of 
the frog in the healthy state. Speaking of the distribution of 
the bloodvessels, Mr. Wharton Jones remarks, that, “ although 
the capillaries all communicate together, a given part of the 
capillary network receives its blood especially from the branches 
of a particular artery, and pours its blood especially into par- 
ticular venous radicles.” 
Structure and Endowment of Arteries. — The walls of the 
arteries are formed of three coats, — the innermost continuous 
throughout the vascular system ; the outermost cellular ; the 
middle muscular. The alterations in the diameter of the 
arteries are effected by contraction or relaxation of the muscu- 
lar coat alone. 
1. Sulphate of atropia being applied, constriction slowly fol- 
lows, the artery slowly regaining its normal width. 
2. Moderate cold, mechanical and galvanic irritation, cause 
rapid constriction, soon succeeded by the normal width. 
3. Solution of sulphate of copper (gr. xv to Jj), with wine 
of opium (3j) dropped on the web, generally causes primary 
dilatation of the arteries. 
4. Concentrated solution of sulphate of copper causes sudden 
dilatation, which slowly yields to permanent constriction. 
Structure and Endowments of Capillaries. — A single coat 
constitutes the wall of the capillaries. “ I have not,” Mr. 
Wharton Jones observes, “ been able to perceive that, when 
capillaries are cut across, their mouths become constricted ; 
much less their canal as a whole. 
Structure and Endowment of Veins. — The smaller veins have 
only one coat, like the capillaries; the larger veins two coats. 
Mr. Jones thinks it must be admitted that the outer coat of 
the larger veins possesses a very slight contractile power. With 
reference to the nerves of the bloodvessels, arteries alone are 
constantly accompanied by nerves, and arteries alone have well- 
marked contractile walls. The ischiatic nerve being divided, 
Mr. Jones found that the arteries of the web retained their con- 
tractility, though they became more dilated than usual. 
After section of a nerve accompanying an artery, constriction 
of the artery took place, but soon ceased. The supervening 
dilatation was greater below than above the injury. 
Chap. II treats Of the Circulation of the Blood in the Web 
of the Frog in the Healthy State. 
Section 1. — Blood of the Frog. — The addition of white of 
egg to a drop of freshly-drawn frogs blood causes the red cor- 
