Abstract

1. It has been definitely shown that the lymph hearts are powerful organs effecting a considerable transference of solutions, after cardiectomy, into certain veins which communicate with the meningeal vessels. Drugs injected into the lymph sacs are readily carried to the spinal cord and brain through these veins. A reversed circulation is thus established in these organs, the solutions of drugs being driven through the veins and capillaries into the arteries.

2. Details of the anatomical routes that are followed by drugs and dyestuffs in their passage to the spinal cord and brain, from both the anterior and the posterior lymph hearts, are discussed in the paper, and drawings and illustrations are given that prove the actual passage of convulsant dyes and even of suspensions, as india ink, by these routes.

3. It has been shown that the posterior lymph hearts may, under certain circumstances, be as effective as the anterior in this transference. Conditions of temperature and activity of the lymph hearts explain the varying results obtained when the anterior lymph hearts only are destroyed. If the posterior lymph hearts are then sufficiently vigorous to carry a convulsant drug to the central nervous system when it is still irritable, convulsions will occur, but otherwise not.

4. Far smaller doses of acid fuchsin than the "minimal surely convulsant dose" of Joseph and Meltzer will produce convulsions when a solution of the dye is dropped directly on the openings of either the anterior or the posterior lymph hearts. As against the minimal dose of 1/20 mg. per gram body weight of Joseph and Meltzer for cardiectomized frogs, we obtain convulsions by the method described, with 1/100 mg. or less per gram body weight. The difference is evidently due to the avoidance of waste in the lymph sacs. The minute dose of the drug required in this experiment is in agreement with our contention that passage through one or more of the lymph hearts, either anterior or posterior, is necessary to reach the spinal cord and brain.

5. When all four lymph hearts are destroyed convulsions can not be obtained in cardiectomized frogs with the doses and within the time limits of Meltzer's and Joseph's Experiments.

6. This negative result is farther supported by experiments in which an eviscerated frog is immersed in a solution of a convulsant drug, and in which it is shown that the destruction of the four lymph hearts entirely prevents the appearance of convulsions.