424 IMMUNO-CATALYSIS 



i. Experiments Cited to Support the Acetylcholine Theory of 

 Anaphylaxis. Antigen provokes general vasodepression in sensitized 

 cats and dogs; it causes the vessels of the paw of dog to dilate; stops the 

 frog's heart; and augments the tonus of the intestine and uterus of 

 the guinea pig and rabbit. Eserine and strophanthin inhibit the action 

 of cholinesterase, permitting the accumulation of acetylcholine. In 

 this manner these inhibitor drugs exaggerate the above effect provoked 

 by antigen. 



A suspension of agar stimulates contraction of the isolated uterus 

 and intestine. This effect is identical with that of acetylcholine. When 

 the organ is eserinized the eflFect is accentuated. Atropine inhibits 

 this effect. The isolated heart of the guinea pig is stopped if suspended 

 in agar solution. Atropine inhibits this effect on the heart. This block- 

 age is not due to potassium ion or histamine; these are still able to pro- 

 duce their effects on atropinized tissue. 



In rabbits, the intravenous injection of 6 ml. of a gelatin solution 

 causes death within two to three minutes. This shock is inhibited by 

 atropine. The injection of 3 ml. of gelatin solution does not produce 

 shock in the rabbit. However, the animal which is subcutaneously 

 eserinized (0.25 to 0.5 mg. of eserine) succumbs to shock wdthin 2 

 minutes when 2 to 3 ml. of gelatin solution are injected intravenously. 

 This shock is due to the liberation of acetylcholine. 



An amount of antigen-antibody complex prepared in vitro which 

 does not produce shock in the guinea pig, produces fatal shock in 

 animals eserinized subcutaneously. It is to be noted that eserine 

 promotes the shock produced by injection of acetylcholine, or an 

 antigen, or a gelatin solution. Atropine inhibits anaphylaxis even in 

 eserinized guinea pigs. 



It is found that strophanthine favors anaphylactic shock because 

 it inhibits cholinesterase and thereby permits the accumulation of 

 acetylcholine. A dose of an antigen-antibody mixture which is in- 

 capable of provoking shock in normal guinea pigs causes fatal shock in 

 strophanthinized guinea pigs. But, if the tissue is rendered refractory 

 to acetylcholine by means of atropine, the same antigen-antibody 

 mixture fails to provoke shock in the strophanthinized and eserinized 

 guinea pigs. 



A large dose of atropine inhibits anaphylactic shock. It is claimed to 

 exercise two principal actions: (a) it inhibits the activity of cholines- 



