Cellular Immunity, 



95 



cat possesses, as compared with the rabbit, a high degree of congenital 

 immunity to cobra venom, the red blood corpuscles of the eat are less resistant 

 to the haemolytic action of the venom than are the red blood corpuscles of the 

 rabbit. 



Acquired Immunity to Cobra Venom. 



The object of these experiments was to determine whether, when an animal 

 is actively immunised to cobra venom, the tissues of the animal, free from the 

 serum, acquire increased resistance to the venom. For this purpose we 

 compared quantitatively the effects of the venom on the heart, intestine and 

 blood corpuscles of an immunised animal with its eifects on the same organs 

 of normal unimmunised animals. 



The difficulty of immunising rabbits to cobra venom is well known and it is 

 not necessary for the purposes of this paper to deal with the question. It is 

 sufficient to state that, of twelve rabbits, which we began to immunise in 

 February, 1920, only one survived immunisation to the degree of tolerating 

 10 minimum lethal doses. This rabbit received the injections intravenously 

 into the marginal veins of the ear. The doses were increased very gradually. 

 It weighed 1420 grm. on February 7, 1920, the day on which it received its 

 first venom injection, and on June 6, 1920, when it received its last 

 injection of 10 M.L.D., it weighed 2580 grm. This last injection caused 

 a fall of weight on the following day to 2450 grm. but the animal recovered 

 its normal weight by June 10 when it was killed and its isolated organs used 

 for experiments. 



The following experiments were performed : — 



(a) Heart. 



In Table I was shown the effect of the venom we were employing on the 

 isolated hearts of normal rabbits. In these experiments perfusion with 

 Locke's solution was carried on for at least 20 minutes to remove all the 

 serum. The same procedure and technique was employed for the heart of the 

 immunised rabbit. 



In the following Table III the heart of the immunised rabbit is compared 

 with the hearts of unimmunised rabbits in respect to their susceptibility to 

 the toxic action of the venom. 



The heart of the immunised rabbit was first perfused with a concentration 

 of venom of 1 in 400,000 for 45 minutes. In this time only a sUght slowing 

 and rise in tone was produced. The concentration of venom perfused was 

 then doubled and arrest in systole was produced in 20 minutes after turning 

 on the new solution. 



When these effects are compared with the effects of the venom on the 



