Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

powerful current, a very firm clot is formed, which adheres to the walls of the artery, and so stops the circulation. This can be accomplished, in like manner, in the veins, but in less degree. If a current of moderate intensity is used, the clot forms in from five to fifteen minutes. The clot forms only at the positive pole, because of the decomposition of the salts of the blood, and the liberation of acid at that pole; while, at the negative pole, the action and decomposition there sets free an alkali, which renders the blood even more fluid than natural. " If the posi- tive electrode of a moderately active galvanic battery is plunged into the artery of a living dog, the blood soon becomes coagu- lated, and that without pain, inflammation, or gangrene ; but if the negative electrode is thrust into the artery, there is no coagu- lation, but rather the blood is rendered more fluid, with pain, inflammation, and sometimes speedy gangrene. Hence, when- ever we wish to coagulate the blood in the vessels, as for vari- cose veins, or in an aneurismal sac, we must employ the positive pole in the sac or vessel, while the negative is simply a large moist surface contact, and so directed to the border of the sac, or vessel, that the current shall pass directly and steadily through it." When galvanism is applied to blood vessels, they are found to contract pretty generally ; but this appears to be much in pro- portion to the number of fibre-cells they respectively contain. Thus the aorta in man scarcely contracts under this influence, because it is mostly made up of elastic fibres, and with but very few contractile fibre-cells. But these fibre-cells are found far more uniform and abundant in the smaller arteries, and conse- quently they are seen to contract energetically, when thus influ- enced. They have a peculiarity of contraction, and that is, as repeatedly observed, only after the current has been acting for a little time, and which effect also continues for a little time after the current is discontinued. Professor Claude Bernard assumes that the capillaries possess two properties, — the one for contraction, the other for dilatation, — and that either of these are brought into their physiological action under the influence of a peculiar set of nerves.