350 PROTECTIVE INOCULATIONS. 



cubic centimetres which had been exposed for one hour to a temper- 

 ature of 60 C. At a temperature of 65 C. both the toxic and the 

 immunizing action is destroyed. 



Behring (1892) gives the following account of a method which he 

 has successfully employed for producing immunity in large animals 

 especially in horses: A culture of the tetanus bacillus is made, in 

 bouillon, of such toxic potency that 0.75 cubic centimetre will kill a 

 rabbit in three or four days. To two hundred cubic centimetres of 

 this culture he adds carbolic acid in the proportion of 0.5 per cent for 

 the purpose of preserving it. The horse first receives a subcutaneous 

 injection of ten cubic centimetres of this culture fluid to which ter- 

 chloride of iodine (IC1 3 ) has been added in the proportion of 0.25 

 per cent; at the end of eight days twenty cubic centimetres of the 

 same mixture are given; again in eight days the dose is repeated; 

 then, after an interval of three days, thirty cubic centimetres of the 

 same mixture. Following this, at an interval of eight days, he gives 

 two injections of thirty cubic centimetres each of a mixture containing 

 one-half the quantity of IC1 3 (0.175 per cent). The proportion of 

 the iodine terchloride is then reduced to 0.125 per cent, and two 

 doses of twenty cubic centimetres each are given. Finally the culture 

 fluid is administered in the dose of 0.5 cubic centimetre, and this dose 

 is doubled every five days. Before giving the first dose of culture 

 fluid without the addition of IC1 3 , the immunizing value of the blood 

 serum of the horse is tested on mice, and if it falls below 1 : 100 a 

 dose of 0.25 cubic centimetre is given instead of the larger dose (0.5 

 cubic centimetre) above mentioned. 



Schutz (1892) has applied Behring 's method to a considerable 

 number of horses and sheep, and arrives at the conclusion that it is a 

 reliable method of protecting these animals against infection with liv- 

 ing tetanus bacilli and against the toxic action of filtered cultures ; 

 that the degree of immunity" and the antitoxic power of the blood 

 serum increase as larger doses are gradually given. According to 

 Behring the immunizing value of blood serum from a horse treated in 

 this way is very high. As tested on mice it may be 1 : 200,000, or even 

 more. According to his calculations a serum having a value of 1 : 100,- 

 000, as tested on mice, should be given to a man weighing fifty kilo- 

 grammes in the quantity of fifty cubic centimetres, given in the course 

 of two days, in order to insure immunity. 



The same author in a subsequent paper (1892) gives details as to 

 the method of estimating the therapeutic value of serum from an im- 

 mune animal. He first calls attention to the fact that the only re- 

 agent by which the antitoxic potency of this serum can be tested is 



