272 TEXT-BOOK OF PHYSIOLOGY. 



heart. In the auricles the bundles are arranged in two sets : an outer 

 transverse set, wmcn pass from auricle to auricle, and an inner longi- 



tudinal set, which pass over the auricles to be attached anteriorly 

 and posteriorly to tin- connective tissue of the auriculo-ventricular 

 groove. The longitudinal fibers of each auricle are practically in- 

 dependent of each other. Circularly arranged fibers are present near 

 the terminations of the veme cavrc and pulmonary veins. 



In^the ventricles the muscle-bundles are also arranged in two 



sets, a superficial longi- ^ 

 tudinal and a 7leep/r rwv 

 transverse, though their 

 arrangement is some- 

 what more complicated 

 than that observed in 

 the auricles. In a gen- 

 eral way it may be said 

 that the superficial lon- 

 gitudinal fibers on both 

 the anterior and poste- 

 rior surfaces from their 

 origin in the connective 

 tissue of the auriculo- 

 ventricular groove pass 

 obliquely downward and 

 forward from right to 

 left toward the apex, 

 where they turn back- 

 ward and inward in a 

 vortex, after which they 

 ascend to terminate in 

 the wall of the septum, 

 the columnar carneae 

 and musculi papillares. 

 Longitudinal fibers are 

 also found on the inner 

 surface. The transverse 

 fibers are very abundant 

 and surround each ven- 



ncle separately. Between the superficial longitudinal and deep 

 transverse fibers there are several layers of fibers which possess 

 varying degrees of obliquity. The general arrangement of the fibers 

 is such as to ensure a complete and simultaneous discharge of blood 

 irom both auricles and ventricles (Fig 120) 



FIG. 120. MUSCLE-FIBERS OF THE VENTRICLES. 

 i. buperficial fibers, common to both ventri- 

 cles. 2. Fibers of the left ventricle. 3. Deep 

 fibers, passing upward toward the base of the 

 he ??'^ 4 ' Fi ^ers penetrating the left ventricle. 

 (Sappey, after Bonamy and Beau } 



