A 1 TURE OF SUBSTANCES CONCERNED IN AGGLUTINATION 179 



in a higher dilution than any micro-organism affected merely by the 

 group agglutinins. It is true that bacteria not injected were at times 

 agglutinated in higher dilutions than the variety injected; this, if not 

 due to greater sensitiveness, was on account of normal group agglu- 

 tinins present in the animal before immunization. In horses and adult 

 goats it was found that before injections were commenced there was 

 often a great accumulation of agglutinins for bacteria and especially 

 for members of the dysentery, paradysentery, and colon groups, so 

 that the estimation of the development of specific agglutinins was a 

 matter of great difficulty except through careful absorption experiments. 

 For this reason untreated horse serum is a very dangerous substance 

 to use in differentiating the intestinal bacteria. This is clearly brought 

 out in the record given of the tests made of two horses. The great 

 height to which the group agglutinins may rise is seen in the following 

 table: 



TABLE I. 



Agglutinin in the Serum of a Horse Injected with Paradysentery Bacillus. 

 Type, Manila Culture. 



After 18 injections. After 21 injections. 



Culture. 1:3000 1:5000 1:10,000 1:3000 1:5000 1:10,000 



Paradysentery type, Manila 4-4- 4-4- 4-4- 



Colon B. X 4-4- 4-+ 4-4- 4-4- 



The great amount of agglutinins acting upon the colon bacillus X. 

 is remarkable. A serum is here seen to be acting in dilutions as high 

 as 1 : 10,000 upon a culture possessing very different characteristics 

 from the one used in the injections. 



Although a considerable proportion of the group agglutinins acting 

 on colon bacillus X was undoubtedly due to the stimulus of the injections 

 of the Flexner paradysentery culture, still a portion of them was prob- 

 ably due to other causes. In Table II. is seen the marked accumula- 

 tion of agglutinins which may occur in a horse before injections are 

 begun and the results of injection nutrient bouillon which had been 

 prepared from meat in the usual way. 



TABLE II. 



A young horse before The same one week after being 



inoculation. injected with one litre of bouillon. 



Culture. 1:100 1:500 1:1000 1:5000 1:100 1:500 1:1000 1:5000 



Dysentery B., Japan . . 4- 4-+ 



Paradysentery, Mt. Desert 4-4- 



Manila . 4-4- 



ColonB. X. ... 4-4-4- + 



The fact of most importance which appears in this table is the abun- 

 dant agglutinins which may be found in the serum of a horse which 

 has never received bacterial injections. 



Three rabbits injected with nutrient bouillon developed agglutinins 

 for the paradysentery and some of the colon bacilli. In one rabbit's 

 serum the Manila culture agglutinated in dilutions of 1 : 150. 



