.■)2 The Precipitins: Methods 



antisera. I have frequently used sera from cadavers, both human and 

 animal, the latter more especially from animals dying at the Zoological 

 Gardens, London. 



As a rule no difficulties ai-e encountered, the rabbits bearing the 

 treatment well, a slight loss of weight being noticeable after the first 

 injections. My experience suggests that it is better to grade the 

 dosage of seinim, as is after all usual in immunization experiments, 

 beginning with a small dose and gradually raising the amount admi- 

 nistered, being guided by the animal's body-weight. It is especially 

 necessary when treating an animal with a serum whose possibly toxic 

 effects are unknown to begin with a small dose. Occasionally accidents 

 will happen, well-immunified rabbits dying, perhaps after the last injec- 

 tion, apparently from intoxication ; this has however happened rarely in 

 my experience. Of the sera injected, I found rabbits to tolerate larger 

 quantities emanating from the horse than from other animals. It 

 therefore seems strange to me that Rostoski (1902, b, p. 26) should 

 have experienced any difficulty when treating rabbits with horse serum, 

 most of his animals dying, and he concludes, " so scheint es mir sehr 

 schwer bezw. unmoglich zu sein, Kaninchen gegen die specifische Gift- 

 wirkung des Pferdeserums zu immunisiren." This is so contrary to the 

 experience of others that I am inclined to attribute it to his simply 

 having used excessive dosage. Even under identical conditions of 

 treatment rabbits of similar weight will yield antisera of different 

 strengths, so that the individual element enters also into the 

 problem. 



Attempts made by myself, and others (Whitney, 1902, etc.), to 

 obtain antiserum after a single injection of blood, or the like, have failed. 

 Michaelis (9, x. 1902, p. 734) states that he only once observed a 

 l)owerful antiserum to have developed in a rabbit bled 14 days after 

 a single injection of 20 c.c. of ox serum, the rabbit's blood having 

 contained no precipitin three days after the injection, and all traces 

 thereof having disappeared three weeks after its presence was obser\'ed. 

 Otherwise all workers have subjected their animals to repeated injections 

 of serum, a varying number of days intervening between each. 



Minovici (12, yi. lf)02) states that ox blood produces precipitin more 

 rapidly than does human blood, an observation which I have not as yet 

 been able to confirm. There is no reason why an animal should not 

 react more rapidly to onr blood than to another, but to establish this 

 requires not a few, but many carefully conducted experiments where 

 the conditions are equal. 



