SENSITISING INJECTION 17 



only in this case the condition of anaphylaxis appears 

 much more slowly than with weak doses. As a 

 general rule anaphylax:is takes a longer time for its 

 production in proportion to the strength of the 

 initial dose of the serum. For instance, if, in order 

 to sensitise it, we inject a guiena-pig with 5 c.c. of 

 serum, we must not be surprised if we fail to see the 

 onset of the anaphylactic state till after the lapse of 

 several months; whereas with the initial dose of 

 o-oi c.c. the ordinary interval hardly exceeds ten to 

 twelve days. 



Therefore, in order to sensitise rapidly and satis- 

 factorily, it is to our interest to employ weak doses. 

 As to strong doses, they, too, certainly sensitise, but 

 only after a long time. Our impression is that, in 

 order to become capable of sensitising, the serum 

 needs to be eliminated to a great extent, either just 

 as it is, or after having undergone a transformation 

 within the animal. It does not become truly active — 

 that is to say, sensitising — till the very moment that 

 it becomes very much diluted in the body. This is 

 one of the most curious peculiarities of anaphylaxis, 

 and, we may add, one that has remained almost un- 

 solved to the present day. 



If weak doses of serum are those that should be 

 ohosen by preference, they must not, however, exceed 

 certain limits. It is true that, according to Rosenau 

 and Anderson, even a millionth of a cubic centimetre 

 of serum is sufficient for sensitisation. We would 

 venture to remark, however, that in our experience 

 when the dose has been less than one-thousandth of 

 a cubic centimetre the results have been very 

 uncertain. 



Rosenau and Anderson state that animals may be 

 sensitised by the intestinal route. By feeding guinea- 

 pigs with horse-flesh or giving them serum to drink 

 they have succeeded in bringing about hypersensi- 



