THE HEART 



147 



two main divisions that we know in the adult. Anatomical dissections have 

 shown that the muscles of the ventricles form spiral sheaths extending from 



FIG. 138. 



FIG. 138. Cardiac Muscle Cells, Showing their Form, Branches, Nuclei, and Striae. From 

 the heart of a young rabbit. Magnified 425 diameters. (Schafer.) a, Line of junction between 

 the cells (intercellular cement) ; b, c, branches of the cells. 



FIG. 139. Cardiac Muscle Cells of the Left Ventricle of a Child at Birth (full term), to show 

 the form of the cells, their structural details, their relations to one another, and their general agree- 

 ment with those of cold-blooded vertebrates. A, Large cell with two nuclei; this cell has nearly 

 the proportions of those of the adult; B, group of cells in their natural relatipn. At the right of 

 the middle cell are two spaces or fissures, n. Nucleus. The transverse striations cross the nuclei 

 in all the cells, and each nucleus possesses several nucleoli. (Gage.) 



FIG. 140. 



FIG. 141. 



FIG. 140. Diagram of the Course 9f the Superficial Muscle Layers Originating in the Right 

 and Left Auriculo- ventricular Rings and in the Posterior Half of the Tendon of the Conus. (After 

 MacCallum.) C, Anterior papillary muscle. 



FIG. 141. Diagram of the Course of the Superficial Muscle Layers Originating in the Anterior 

 Half of the Tendon of the Conus. (After MacCallum. ) A , Posterior papillary muscle; B, papillary 

 muscle of the septum. 



