330 Mr Myers, The Standardisation of Antivenomous Serum. 



A cheap and susceptible animal is desirable. Now it is clear 

 that with equally susceptible animals, that is with animals for 

 which the minimal lethal dose per gram weight is the same, the 

 smaller the animal, the smaller will be the differences that can 

 be observed in the neutralising power of the antitoxin, since 

 with snake poison, we can only distinguish between mixtures of 

 toxin and antitoxin that are fatal and non- fatal. The larger the 

 maximal non-fatal dose, the greater is the error therefore. For 

 the same reason, the test dose should be a multiple of the 

 minimal lethal dose, and as large a multiple as possible. 



Amongst common laboratory animals, guinea-pigs and mice 

 seemed to be the most suitable. Guinea-pigs however cannot be 

 used. For to neutralise a multiple of the minimal lethal dose, 

 undiluted serum must be used, and, as Cobbett 1 has shewn, 

 antivenomous serum is very often acutely toxic for these animals. 



This serum is also often toxic for mice, but I have found that 

 death from it does not occur within the first 24 hours, so that if 

 the results be noted for this space of time, we can neglect the 

 toxic action of the serum. Antivenomous serum, as some speci- 

 mens of normal horse serum do, often kills mice in from 4 — 6 days. 



Using mice of about 15 grams in weight then as test animals, 

 and unheated Cobra venom, it was found possible to determine 

 the minimal lethal dose to within 20 °/ , that is increments 

 of 1 in 5 could be appreciated. The minimal lethal dose I found 

 to be '012 mgrms. This dose killed in from 3 — 4 hours. 



Taking ten times this quantity, namely '12 mgrms., the amount 

 of serum required to neutralise it was then determined, the 

 mixtures being allowed to stand at room temperature for half- 

 an-hour. 



The neutralisation of ten times the lethal dose could be 

 estimated to within 15 / o ; when the doses of serum were made 

 closer, the series became irregular, and it was found impossible to 

 distinguish within this limit. 



On comparing the two methods, the method of mixing in vitrio 

 and testing the mixtures on mice was found to be more accurate 

 than the rabbit method as used by Calmette. 



Thus with rabbits of about 2000 grams, 0"5 mgrm. per kilo of 

 the dry venom employed killed in 20 minutes. 



When 0*3 c.c. serum per kilo had been injected 5 minutes 

 previously, the animal died in an hour and a half. With 04 c.c. 

 serum and more, the animals lived and shewed no symptoms. 

 0"5 mgrm. of venom is here neutralised by 0'4 c.c. of serum. Hence 

 0*12 mgrms. would be neutralised by 0'096 c.c. of serum. 



With mice, however, using the same serum, 0*2 c.c. was required 



1 Proceedings of the Physiol. Soc. 1899. 



