Cellular Immunity. 



89 



Table I. — Comparison of the Action of Cobra Venom on the Perfused Heart 



of the Eabbit and Cat. 



Strengtli of solution. 



Rabbit. 



Cat. 







1 in 5,000 

 10,000 

 20,000 

 50,000 

 „ 100,000 

 „ 200,000 

 400,000 

 600,000 

 800,000 

 „ 1,000,000 

 ., 2,000,000 



Systolic arrest in 8 minutes 

 8 „ 

 8 „ 

 „ 10 „ 

 .) 15 J. 

 13 „ 

 15 „ 

 20 „ 

 34 „ 



Systolic arrest in 73 minutes 



Systolic arrest in 7 minutes. 



Systolic arrest in 11 minutes. 

 „ 17 „ 

 ij » 31 „ 

 J) >)_ 34 ,, 

 Not arrested in 80 minutes. 



80 „ 

 „ 105 „ 



This table shows clearly that the heart of the cat is much less susceptible 

 than that of the rabbit to the action of the venom. This does not appear 

 with high concentrations, e.g., there is no appreciable quantitative difference 

 in the action on the rabbit and cat heart in concentrations ranging from 

 1 in 5000 to 1 in 100,000. With lower concentrations, there is an 

 unmistakable difference in the susceptibility of the hearts of the two 

 species of animals, whether this be judged from the time required to 

 produce a given effect, or from the minimum concentration required to kill 

 the heart in systole. Thus, 1 in 200,000 arrests the heart of the cat in 

 31 minutes, whereas half that strength (1 in 400,000) arrests the rabbit's 

 heart in half the time. Or a strength of 1 in 200,000 produces practically 

 the sanle effect on the cat's heart as one of 1 in 800,000 on the rabbit's. 

 Judged from this standpoint, the immunity of the cat's heart is to that of the 

 rabbit's as 4:1. Further, a solution of 1 in 2,000,000 arrests the rabbit's 

 heart in 73 minutes, whereas a solution of 1 in 800,000 does not arrest the 

 cat's heart in 80 minutes. 



In figs. 1 and 2, the effects of 1 in 600,000 are shown on the hearts of the 

 rabbit and cat. The rabbit's heart is completely arrested in 20 minutes, 

 whereas the cat's heart is not markedly affected in 70 minutes. 



It is clear, therefore, that the cat's heart, as compared with the rabbit's, 

 possesses in itself a tolerance to cobra venom. A larger number of experi- 

 ments would be required to give an exact numerical ratio to the difference in 

 susceptibility, if, indeed, it would even then be possible in such experiments 

 to give exactly such a ratio. For the present purpose, it is sufficient to 

 establish the fact that the difference is pronounced, and that, judged from an 

 arbitrary end-point, it requires four times as strong a solution to produce a 

 given effect on the cat's heart as is required to produce that effect on the 

 rabbit's. 



