SECTION V. 



ISOPRECIPITINS. 



The occurrence of isoprecipitins analogous to isohaemolysins dis- 

 covered by Ehrlich and Morgenroth (see p. 42) appears to have been 

 observed by Schiitze (12, xii. 1901, and 6, xi. 1902, p. 804), who obtained 

 them by injecting animals with the serum of other individuals belonging to 

 the same species. Schiitze treated a rabbit every two to three days with 

 5 to 10 c.c. of the serum of other rabbits, administered subcutaneously, 

 until a total of 60 c.c. had been given. The treated rabbit was bled 

 six days after the last injection, and its serum tested for isoprecipitin upon 

 the sera of 32 different rabbits. Of these 32 sera only two reacted, 

 precipitations occurring in 30 minutes at 37 ° C. The reaction was 

 " strictly specific," for, upon the addition of 2 to 4 c.c. of the treated 

 rabbit's serum to 3 c.c. of normal guinea-pig or human serum, no reaction 

 was observable after two hours under the same conditions of temperature. 

 Granted that the reaction took place as stated, it seems somewhat 

 premature to conclude as to the strictly specific character of the reaction 

 after only testing two other non-homologous bloods, even that of the 

 guinea-pig being but distantly related, not to mention the human blood. 



Schiitze (p. 804) states that he found it more convenient to obtain 

 isoprecipitins from goats treated with goat's milk. To do this, he 

 injected 40 — 50 c.c. of the milk every 4—5 days, until a total of 400 c.c. 

 had been administered in the course of a month. Bled eight days after 

 the last injection, the goat yielded a serum which, when added in the 

 proportion of 0"5 to 1 c.c. — 5 c.c. of a 1 : 40 dilution of goat's milk, 

 gave an immediate reaction. 



Evidently then, there would appear to be individual differences in 

 the chemical constitution of different individuals, dcnionstrable by means 

 of isohaemolysins and isoprecipitins. 



