THE PYOGENIC COCCI 163 



the disease. The symptoms disappeared after about ten days 

 and they then reinoculated him over the same area and again 

 obtained the same result. Ten successive attacks were produced 

 in the same manner, which proved, at least, that immunizing 

 substances were not present in sufficient amounts to afford pro- 

 tection. It is a well-established fact that opsonin is increased 

 and phagocytosis consequently active in all infections with the 

 pyogenic cocci. 



A degree of active immunity may be produced in rabbits and 

 horses by inoculating them with gradually increasing doses of 

 streptococcus cultures. Experiments with animals have shown 

 that the serum from such immune animals will protect to a cer- 

 tain extent against the organism used for its production, but not 

 against other strains. 



Accordingly, in order that the serum may contain antibodies to 

 combat the different streptococcic infections, a number of different 

 strains isolated from different forms of disease are used for inocu- 

 lating the horses. The " polyvalent " serum obtained from ani- 

 mals so treated is not so efficient as one prepared from the organisms 

 infecting the treated case, but it is moderately effective for all cases. 

 The use of such serum seems to have been of benefit in certain 

 cases, but on the whole the results have been disappointing. Large 

 doses must be given in order to obtain a sufficient amount of anti- 

 bodies to produce an appreciable effect. 



Vaccines are administered in subacute conditions. The initial 

 dose is 5 to 10 million organisms; increasing amounts may be 

 given to 500 million as a maximum. 



