The nervous coördination of the auricles and ventricle of the heart of the lizard

The following investigation was carried out on the hearts of lizards (Ocellata lacerta) for the purpose of studying the nature of conduction between the auricles and ventricles in these animals. The experimental part was done at the Zoölogical Station of Villafranca. Ligatures were applied between auricles and ventricle and the pulsations counted before and after. The histological examination of stained serial sections was made later in the Physiological Institute of Bern.

An abbreviated protocol will illustrate the experimental results.

October 4, 1907. The beating heart of a large lizard whose brain was destroyed, was turned over within the open thorax so that the dorsal surface, where the chief nervous connections between auricles and ventricle are to be found, was lying upward. Whitish cords connect the auricles with the ventricle; the left cord is finer than the right and not always distinguishable. Besides these cords only connective tissue can be noticed between auricles and ventricle.

The heart was beating 25 times a minute, auricles and ventricle beating in regular sequence. After ligating the right cord the ventricle stopped beating for one minute, while the auricles continued to beat irregularly. For minutes later the auricles were beating 18 times and the ventricle 10 times a minute. Later counts gave the following relations : 24 to 12, 24 to 18, 22 to 16. Twenty minutes after ligature the auricles were beating 25 times and the ventricle 22 times a minute. After ligating the left cord also, auricles and ventricle stood still for about one minute, when both began to beat. Again the relations were 10 to 3, 10 to 5, and 14 to 6.

Other experiments gave constantly similar results.

Kronecker and Spalitta observed in Palermo similar incoordination after applying ligatures to the heart of a sea turtle, but the results were not constant.