. The anatomy of the frog. Frogs -- Anatomy; Amphibians -- Anatomy. THE HEART. 219 Fig. 139- rod-shaped, 2'^ to y^ ij. broad and 25 to 43 ju in length. The ratio of length to breadth varying from 1:8 to i : 16. These cells are more frequent in the right half of the base of the ven- tricle than the former variety. In the trabeculae the second variety is more numerous (Pohl-Pincus). The muscle-fibre may be simple (Fig. 141 a 31) or possess branches (Fig. 138); the fibres are all more or less spindle-shaped, and striated transversely and longitudinally, but possess no sarcolemma. The protoplasmic
. The anatomy of the frog. Frogs -- Anatomy; Amphibians -- Anatomy. THE HEART. 219 Fig. 139- rod-shaped, 2'^ to y^ ij. broad and 25 to 43 ju in length. The ratio of length to breadth varying from 1:8 to i : 16. These cells are more frequent in the right half of the base of the ven- tricle than the former variety. In the trabeculae the second variety is more numerous (Pohl-Pincus). The muscle-fibre may be simple (Fig. 141 a 31) or possess branches (Fig. 138); the fibres are all more or less spindle-shaped, and striated transversely and longitudinally, but possess no sarcolemma. The protoplasmic contents of the cell are finely granular; the nucleus mvich more coarsely granular and possessing one or more distinctly marked nucleoli. The striations are due to the presence of a network, which has been carefully described by Messrs. B. Mel- land and C. F. Marshall^, and is similar to that of ordinary volmitary muscle (see histology of muscle).] b. The nerves of the heart. The nervous supply of the,heart is derived from the sympathetic system and from the cardiac branches of the pneumogastric nerve ; the course of which has already been traced (page 175) to the roots of the anterior caval veins, where they form a simple plexus by means of a connecting link (Fig. 139). The plexus possesses nerve-cells and sends off two nerves into the auri- cular septum ; the one (c/) lies dor- sally and is shorter and thicker than the other (v), which lies ventrally in the septvim. They course back- wards to the posterior border of the septum, and there distribute fine branches to the base of the ventricle and surrounding parts. [In the whole of their course in the heart they have numerous nerve-cells, either imbedded be- tween their fibres or attached to the nerves and their branches. The nerve-fibres are both me- dullated and non-medullated. The nerve-cells (Figs. 139, 140,141) ' I have had opportunity of examining Mr. Marshall's slides and have convinced myself of the correctness of his
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