Fig. 6. — Isolated heart of immunised rabbit perfused with cobra venom,; 1 in 400,000. Showing that the 

 toxic effect on the heart of the normal rabbit is far greater i than that produced, by twice as high a 

 concentration, on the heart of the immunised rabbit. 



maximum to a 50 per cent, increase 3 minutes after the venom perfusion 

 began. It would be unwise to lay stress upon a single experiment of this 

 kind, but it is none the less suggestive that the preliminary increase of 

 coronary flow occurs in the cat's heart, which shows a relative natural 



