THE RENDERING OF ANIMALS IMMUNE. 121 



dose of antiveiiene, it was found that doses of 1 c. cm., 2 c. cm,, and 3 c, cm, 

 per kilogramme failed to prevent death, but that 2'5 c. cm. and 3 c. cm, per 

 kilogramme were able to do so. 



In the third series the experiments have as yet been made with only the 

 minimum lethal of cobra venom, and they show that 4 c. cm. per kilogramme 

 of this antivenene is able to prevent death when given thirty minutes before 

 the venom. 



In the fourth series, where the results are likely to give the clearest indica- 

 tions of the antidotal value of antivenene, it was found that recovery occurred 

 in the experiments in which 1*5 c. cm,, 1 c, cm., and 0'8 c. cm. per kilogramme 

 of antivenene were injected thirty minutes after a certain minimum lethal dose 

 of venom ; but that the antivenene was insufficient in quantity to prevent 

 death when 0'75 c, cm. per kilogramme or less was administered. In this 

 series, further, it was found that 5 c. cm, per kilogramme of antivenene was a 

 sufficient dose to prevent death after twice the minimum lethal dose of venom, 

 but that 2 c, cm., 2'5 c. cm., and 3 c, cm. per kilogramme were insufficient. 



The experiments of this series are especially interesting, as nearly all the 

 animals showed symptoms of poisoning before the antivenene had been 

 administered. In each of the fatal experiments the duration of life was 

 greatly prolonged by the administration of antivenene ; and it is probable 

 that in many instances a second injection of antivenene, made half an hour or 

 an hour after the first, would have prevented death. 



It has thus been established, on the clearest evidence, that the blood serum 

 (antivenene) of animals protected against large lethal doses of venom is able, 

 in varying conditions of administration, perfectly to prevent- lethal doses of 

 the venom of the most poisonous of serpents from producing death in non- 

 protected animals. 



In order to obtain some evidence bearing on the question as to whether 

 the more powerful antivenene is produced by the long-continued administra- 

 tion of small non-lethal doses of venom, or by the administration of doses 

 gradually increasing until a large lethal dose is reached, a few experiments 

 were made with the serum of a rabbit which had received one-tenth of the 

 minimum lethal dose nearly every two days during a period of three months 

 and one week, and also of one which had received the one-fourth part of the 

 minimum lethal dose nearly every four days during a period of three months 

 and three weeks, I did not find that the antidotal power of the antivenenes 

 obtained from these animals was great, or nearly so effective as the antivenenes 

 obtained from animals which had finally received a dose much in excess of 

 minimum lethal. When mixed with venom and then injected, 3 c, cm, per 

 kilogramme of these antivenenes was insufficient to prevent death from some- 

 what more than the minimum lethal dose of venom, but 5 c. cm, per kilo- 

 gramme were sufficient to do so, 

 16 



