384 BIOLOGY OF PNEUMOCOCCUS 



sented no serological evidence of the presence of antitoxin in the 

 serum of the immune animals. In addition, serum from normal 

 horses, sheep, rabbits, and chickens, as well as antipneumococcic 

 serum or pneumococcic antibody solution, was found to possess 

 little power to prevent the lung changes or cutaneous reactions 

 evoked in mice by the toxin. 



Clowes, Jamieson, and Olson (1926), 244 by injecting rabbits, 

 sheep, and horses with progressively increasing doses of sterile 

 toxic extracts prepared by the sodium ricinoleate method of Lar- 

 son, obtained a serum that neutralized the skin-reacting substance 

 contained in the extracts, and suggested as a provisional unit of 

 antitoxin the amount of serum required to neutralize one million 

 skin-test doses of toxin. Concentration of the immune serum ef- 

 fected the removal of 99.9 per cent of the total serum-protein 

 without appreciable loss of antitoxin. Larson, 788 in the same year, 

 administered an immune serum prepared and tested in the same 

 manner to patients ill with lobar pneumonia and, because the pa- 

 tients showed a rapid drop in temperature and experienced relief 

 of subjective symptoms following the administration of the serum, 

 he believed that the serum actually contained antitoxin. 



The work of Parker (1929), 1061 referred to earlier in the text, 

 has a definite bearing on the question of the possible existence of 

 pneumococcal antitoxin. Serum prepared by the author in rab- 

 bits and horses by using sterile filtrates of pneumotoxin as anti- 

 gens, under certain conditions, protected guinea pigs against the 

 pneumonia caused by the intratracheal injection of living pneu- 

 mococci and toxic pneumococcal autolysates. The protection thus 

 conferred was heterologous for type and appeared to be due to 

 some immune substance other than protective antibodies, since the 

 latter could not be demonstrated in the active serum of rabbits 

 and horses immunized with sterile filtrates of toxic autolysates of 

 Pneumococcus. In a second publication, Parker and McCoy 

 (1929) 1062 described a method for standardizing the potency of 

 antitoxic horse serum and set as the unit of toxin the amount of 



