Cause of Death of Toads after Destruction of their Lymph Hearts

Abstract

Destruction of the 4 lymph hearts of batrachians produces marked disturbances in lymph circulation, leading to rapid death, as we have repeatedly demonstrated in some 500 toads (Bufo arenarum Hensel) and frogs (Leptodactyllus ocellatus (L.) Gir.). The anterior and posterior lymph hearts are easily destroyed by dorsal route approach under ether anesthesia and cauterizing with a thermocautery. The operation requires 2 to 3 minutes and when the effects of anesthesia have worn off, the animals appear entirely normal, and may be put in sinks kept damp by running water. All the toads in which the 4 lymph hearts were destroyed at one operation died before the 4th postoperative day in winter, and before the 3rd in summer. Mortality during the first 2 days was 87% of all operated animals. Longer survival seems due to incomplete operation. The weight of the toads was found to increase progressively from operation to death at the rate of 20% daily. At necropsy, an enormous accumulation of fluid was observed in the lymph spaces, the peritoneal cavity, and the tissues. This fluid retention seems to be enough to account for the increase in weight of toads (Table I). Presence of a single lymph heart seems sufficient to maintain toads for an indefinite period of time without apparent symptoms. It was observed that if 3 of the lymph hearts were destroyed at one operation and the fourth a week later, survival was more prolonged than when all 4 hearts were destroyed simultaneously. In one group of 7 toads, operated upon in 2 stages, 2 animals continued to live for 2 months while the others survived for 2, 5, 9, 11, and 12 days respectively. This prolonged survival was accompanied by little or no increase in body weight. It is possible that in these cases the ciliated funnels of the peritoneum, well studied by Rugh, permitted the establishment of an active circulation between lymphatics and veins. The studies of Pascualini on absorption of substances injected under the skin, have demonstrated that the reabsorption of fluid takes place by way of the lymph hearts and blood capillaries, the former being more important. Substances of high molecular weight such as inulin and hemoglobin pass into the circulation by way of the lymph hearts. On the other hand, those of low molecular weight such as glucose, sodium chloride, and strychnine pass both by way of the blood capillaries and the lymph hearts. Destruction of the lymph hearts therefore impedes the absorption of substances of the first group only.