118 



PKACTICAL PHYSIOLOGY 



and prevents the escape of the water. Lay open the left ventricle in 

 the same manner as the right, carrying the first incision down the left 

 side of the ventricle. Observe the entrance into the aorta and then lay 

 this open. Note the orifices of the coronary arteries from the right 

 and left sinuses of Valsalva. 



Scratch away the endocardium and look for the auriculo-ventricular 

 bundle along the top of the interventricular septum on each side. The 

 right and left septal divisions are clearly seen as whitish bands in the 



FIG. 115. Right auricle and ventricle of calf. (Keith.) 



1, Central cartilage ; 2, main bundle ; 3. A.V. node ; 4, right septal division ; 

 5, moderator band ; 8, orifice of coronary sinus. 



sheep's heart. Twigs from the bundle pass by way of the columnae 

 carneae into the musculi papillares and reach all parts of the heart. The 

 bundle starts from the A.V. node at the base of the interauricular 

 septum on the right side, and is in connection with the sino-auricular 

 node which is supposed to initiate the rhythm. The nodes are 

 made up of peculiar branched cells ; Purkinje fibres form the bundle. 

 Section of the bundle interrupts the normal sequence of the heart 

 chambers. 



Demonstration of Action of Valves in the ox or horse's heart. 

 (Gad.) Two brass tubes with glass windows are tied one (7 cm. in 



