THE PHENOMENA OF ANTITOXIN FORMATION 63 



or six weeks. It is then heated to 65 C. for half an hour and 

 filtered. It gives rise to marked febrile reaction and but little 

 local reaction. The initial dose is 200 to 300 c.c. 



In giving these large doses the most convenient method is to 

 use a large wash-bottle, the side of which is graduated in 

 cubic centimetres. To the outflow arm there is attached 2 or 

 3 yards of pressure tubing, in the farther end of which a strong 

 exploring needle is inserted, and firmly wired in place. The 

 pressure is obtained by means of a bicycle pump attached to the 

 inflow tube of the wash-bottle by means of pressure tubing. 

 There should be a lateral branch communicating with a mano- 

 meter, by which the pressure can be regulated. Very high 

 pressure is sometimes necessary, especially in the later stages of 

 the process, when the subcutaneous tissues of the horse's neck 

 become sclerosed and dense from the repeated injections. The 

 apparatus is most easily sterilized by passing strong carbolic 

 lotion through it. 



On testing the blood-serum from time to time, it is found that 

 the amount of antitoxin gradually rises, each injection being 

 followed by an increase in the antitoxic value of the serum. Thus 

 the process is a cumulative one, the antitoxic level being raised 

 step by step until a certain height is reached. This height differs in 

 different animals. Thus Atkinson, in summarizing his experience 

 of 100 horses, found that half of this number gave less than 

 300 units of antitoxin per cubic centimetre, a quarter between 

 300 and 500, whilst three gave more than 800. There appears 

 to be no method of investigation by which the value of a horse 

 as a source of antitoxin can be predicted early in the course 

 of treatment, and the great variability amongst different animals 

 is probably the reason that different observers have come to 

 such divergent opinions as to the best doses to give and the 

 most suitable intervals between each. Here are three chief 

 methods : 



(a) By the use of large doses of toxin, 250 to 500 c.c. every day, 

 or almost every day, leaving an interval of a week or ten days 

 before the bleeding, so as to allow the last injection to produce its 

 maximum effect. 



(b) The use of large injections (similar to the former) at longer 

 intervals five to ten days. 



(c) The use of relatively small doses of weak toxins repeated 

 every day. 



