360 STREPTOCOCCIC INFECTIONS 



Apart from this, the existence of a soluble toxin is doubtful. 

 Filtered broth cultures of the organism are poisonous, but 

 most observers have been^able to produce immunity therewith, 

 and the toxic substances are probably merely simple metabolic 

 products. Parascandalo, it is true, claimed to have been more 

 successful, but his results have not been corroborated, and there 

 is some reason to believe that the nitrate which he used was not 

 free from bacteria, living or dead, and that his animals were 

 really vaccinated with a vaccine. The toxin is probably an 

 endotoxin, though of this but little is known. The bodies of the 

 bacteria are highly irritating, and very small doses of vaccines 

 have to be given at the commencement of the treatment. 



Diagnosis. This is made by the demonstration of the micro- 

 organism in all cases. Agglutinating sera may be prepared, 

 but the appearance of the property in the serum in human 

 disease is not sufficiently marked or constant to be of value. 



Immunity. Human blood appears to contain an antilysin which 

 neutralizes the action of streptocolysin, and it is quite possible 

 that this substance may play some part in the defence of the body 

 against infections. There is also a little evidence for the forma- 

 tion of a true antitoxin against the actual and efficient toxin of the 

 streptococcus, whatever this may be. This is the fact that in 

 some cases, though unfortunately not in all, the injection of anti- 

 streptococcic serum is followed by a marked immediate benefit in 

 cases of septicaemia, etc. The temperature may fall, the delirium 

 and headache pass off, and the pulse improve in a striking manner 

 within an hour or two of the injection. Now Wright has pointed 

 out that but little is known of the mode of action of the serum, 

 and that it may contain a toxic ingredient and really be a vaccine 

 in disguise. If this is the case we should not expect it to produce 

 good effects so early as actually happens in favourable cases, in 

 which its action resembles that of diphtheria antitoxin, and 

 certainly suggests that some poison is neutralized. Probably, 

 therefore, acquired immunity to streptococci is partly antitoxic or 

 anti-endotoxic. 



Bacterial immunity is probably mixed, partly bactericidal or 

 bacteriolytic and partly phagocytic. The serum of normal 

 animals has usually some bactericidal action, and this can be 

 raised by immunization to a high figure ; further, the serum of a 

 immunized animal is a powerful agent in conferring passive 

 immunity, a property not belonging (apparently) to sera of high 



