Abstract
Method—Gracilis muscles in anesthetized dogs were injected with India ink introduced under pressure centrally into the femoral artery below the origin of the branch artery to the muscle without interrupting the circulation. The injection was continued until the venous blood showed complete blackening. The muscle was quickly clamped off, excised, and dropped at once into Bouin's fluid for fixation. Paraffin sections about 10 to 15μ thick were made for counting. To study the effect of exercise, a muscle was stimulated directly through the obturator nerve by means of brief tetani repeated about once a second for about 3 to 5 minutes. India ink was injected while the muscle was being stimulated.
Results on muscles of amytalized dogs. In resting gracilis about 925 capillaries were injected per sq. mm. of tissue. These are figures for injected bundles. There were also many bundles in which larger vessels contained ink but capillaries none. In exercised gracilis about 1900 capillaries were injected per sq. mm. tissue. An occasional uninjected bundle was seen in these muscles, but far fewer than in resting muscles.
Ratio 1900/925 = 2.05
The maximum number of capillaries per sq. mm. (about 2200) was seen in muscles injected 1/2 hour after death. No uninjected bundles were seen.
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