90 Messrs. J. A. Gunn and R. St. A. Heathcote. 



Fig. 1. — Isolated rabbit heart perfused with cobra venom, 1 in 600,000. 



Fig. 2. — Isolated cat heart perfused with cobra venom, 1 in 600,000. Showing that whereas tie 

 rabbit heart is completely arrested ia systole in 20 minutes, the cat heart is not markedly affected 

 in 70 minutes by the same strength of solution. 



(b) Coronary Blood-vessels. 



When either the rabbit's or the cat's heart is perfused with solutions of 

 cobra venom, the flow through the vessels is markedly diminished as soon as 

 the ventricle goes into systolic contraction. This effect occurs with other 

 substances, which produce rigor of the heart muscle. The flow is stopped by 

 compression and indirect occlusion of the vessels, as the result of the 

 contracture of the heart muscle surrounding them. 



