Cellular Immunity. 



91 



The chief point of interest lies in the effect of the venom on the coronary 

 flow prior to the onset of rigor of the heart. In the rabbit, the flow always 

 diminishes from the beginning, independently of the alteration in the heart 

 beat. The effect is therefore no doubt a direct action on the arterial wall, 

 similar to that which occurs with other types of smooth muscle, and which 

 will be dealt with in the next section. In the cat, on the other hand, there 

 is generally a preliminary increase in the coronary flow, sometimes to the 

 extent of over 50 per cent., which may last for several minutes. This, again, 

 is independent of changes in the heart's contractions, and is therefore 

 probably due to the venom causing a preliminary dilatation of the coronary 

 arteries. The eifect is not constant, and in its nature and occurrence 

 resembles the effect produced by the venom on the smooth muscle of the 

 intestine, which in the cat is sometimes relaxed by the venom. 



The conclusions we draw from these experiments are (1) that the heart 

 muscle of the cat is much less susceptible to the toxic action of the venom 

 than is the heart muscle of the rabbit, and (2) that there is a qualitative 

 difference in the reaction of the coronary arteries of the two species of 

 animals, those of the cat being usually at first relaxed by the venom, those 

 of the rabbit always contracted from the beginning. 



(c) Intestine. 



A large number of experiments were performed to compare the effects of 

 cobra venom on the intestine of the rabbit and of the cat. These experi- 

 ments were performed by the now familiar method of Magnus, sections of 

 the small intestine, about 2 cm. in length, being suspended in a bath of 

 oxygenated Locke's solution at 37° C. The bath contained 50 c.c, and the 

 venom was added in solution in known amounts, so that the resulting 

 concentration of it could easily be calculated. 



For the purpose of an investigation like the present, the intestine does 

 not give such reliable quantitative results as the perfused heart. When the 

 heart is perfused, the venom acts uniformly throughout the substance of the 

 heart muscle, whereas when the venom is added to the solution surrounding 

 the suspended intestine, the action to begin with is a superficial action. 

 Substances which act on the nerve-endings, like pilocarpine or adrenaline, 

 exert their actions almost instantaneously on the isolated intestine when the 

 effects are recorded in the manner here adopted. With substances that act 

 on the muscle, like cobra venom, which is also probably slowly diffusible, there 

 is a definite delay in the production of the full effect of a certain concentra- 

 tion on the isolated (non-perfused) gut, a delay due to the fact that the 

 venom reaches superficial muscle fibres before deeper ones. 



TOL. XCU, — B. H 



