60 A Ma u mi I of Vetervna/ry Physiology. 



heart, but rather that this is due to changes taking place 

 in the muscle itself ; and he calls especial attention to the 

 cellular and protoplasmic features of the heart's muscle in 

 support of this statement, likening the contraction of 

 cardiac muscle to the spontaneous movements of undif- 

 ferentiated primordial protoplasm. 



When life is suddenly destroyed in horses by shooting 

 through the head, it is not uncommon for the heart to 

 continue beating for one or two minutes. Colin divided 

 the spinal cord in a horse and established artificial respira- 

 tion, fifteen minutes after the operation the heart was 

 beating 42 to the minute, and it did not cease contracting 

 for 50 minutes after the section. In another case the cord 

 and both pneumogastrics and sympathetics were divided ; 

 artificial respiration being established the heart beat for 

 24 minutes. In a third experiment the animal was 

 decapitated and both carotids tied ; artificial respiration 

 being established the ventricles contracted for 17 minutes, 

 and the auricles for 34 minutes. 



Ganglia are found in the heart — in the frog two are well 

 defined, known as Remak's and Bidder's ganglia. In 

 mammals ganglia are found in the venae cavse and pul- 

 monary veins, also in the walls of the auricles, auriculo- 

 ventricular groove, and in the base of the ventricles. The 

 auricular septum in its central parts is free from ganglia 

 (Foster). The cardiac nerves, viz., the vagus and fibres 

 from the sympathetic, form plexuses around the aorta. ( hie 

 of the theories of the cause of left laryngeal paralysis in 

 horses, is that based on the anatomical position of the left 

 recurrent nerve relative to the aortic trunk and bronchia] 

 glands. Aortic compression and bronchial glandular en- 

 largement are the assigned causes of the muscular atrophy 

 of the larynx. 



The right vagus nerve is said to have more influence 

 over the heart, than the left. 



It would be outside the scopo of this work to enter more 

 fully into the nervous mechanism of the heart, particularly 

 that dealing with the nature and causes of contraction, hut 



