440 IMMUNITY. 



Some further facts about anti-tetanic serum are given on 

 page 365. 



Use of Antitoxic Sera. In all cases the antitoxic serum 

 ought to be injected as early in the disease as possible, and 

 in large doses. In the case of diphtheria 1500 immunity 

 units of antitoxic serum was the amount first recommended 

 for the treatment of a bad case, but the advisability of using 

 larger doses has gradually become more and more evident. 

 Sidney Martin recommends that as much as 4000 units 

 should be administered at once, and that if necessary this 

 quantity should be repeated. The strongest- serum prepared 

 at present by Behring contains 3000 units in 5-6 c.c., but, 

 as already stated, there is now a good prospect of obtaining 

 a more powerful serum easily. Even very large doses of 

 antitoxic serum are without any harmful effects beyond the 

 occasional production of urticarial and erythematous rashes. 

 Where large quantities of serum require to be administered, 

 as is always the case with anti-tetanic serum, injections 

 must be made at different parts of the body ; preferably 

 not more than 20 c.c. should be injected at one place. 

 The immunity conferred by injection of antitoxic serum lasts 

 a comparatively short time, usually a few weeks at longest. 



Sera of Animals immunised against Vegetable and Animal 

 Poisons. It was found by Ehrlich in the case of the vege- 

 table toxines, ricin and abrin, and also by Calmette and 

 Fraser in the case of the snake poisons, that the serum of 

 animals immunised against these respective substances had 

 a protective effect when injected along with them into 

 other animals. Ehrlich found, for example, that the serum 

 of a mouse which had been highly immunised against ricin 

 by feeding as described above, could protect another 

 mouse against forty times the fatal dose of that substance. 

 He considered that in the case of the two poisons, anta- 

 gonistic substances "anti-ricin " and "anti-abrin" were 

 developed in the blood of the highly-immunised animals. 

 A corresponding antagonistic body, to which Fraser has 

 given the name anti-venin, appears in the blood of animals 

 in the process of immunisation against snake-poison. 



