164 



H. E. JORDAN AND K. B. STEELE 



10. Trout 



In heart muscle of trout (fig. 19, representing several levels 

 of focus), the discs are distinctly fewer in number than in higher 

 groups. Occasionally also the oval type appears as thickenings 



18 \..s 



Fig. 18 Cardiac muscle of frog. 

 Fig. 19 Cardiac muscle of trout. 



19 



The intercalated discs are similar to the 



simpler types of hearts of higher forms, but distinctly less numerous. 



on the more distinct stouter (contracted) fibrils. The relation 

 with respect to the nuclei and the anisotropic bands is the same 

 as described for higher vertebrates. The discs are more abundant 

 in contracted (darker) regions, and near branches. Occasionally 



