A graphite suspension for intravital injection of capillaries

In the ordinary use of injection masses the observer expects to fill and obstruct vessels, and the injection is considered successful in the degree to which it seems to fill the maximal number of available paths. In contrast to this relatively simple procedure is found an increasing number of attempts to inject a living tissue in such a manner as to fill all the vessels transporting blood at the moment when the normal circulation is interrupted. Noteworthy among such applications of injection technique to physiology are the contrasting injections of resting and active muscle made by Krogh (1) in 1919. In these experiments frogs and guinea-pigs received a suspension of India-ink by vein, and this material, mixed with the blood of the animal, was pumped to the capillaries by the heart. Results obtained in this way constitute single terminal observations, since capillary obstruction begins to take place practically at once.