THE PNEUMOCOCCUS 321 
to 1 cc. in rabbits, 0.1 to 1 cc. in guinea-pigs, produced death when 
injected intraAenously or intraperitoneally. The toxicity of the 
filtrate was roughly proportional to the \'irulence of the organisms for 
rabbits. Heating the filtrate to 00° C. for an hour, or exposure to 
chloroform vapor for the same time reduced the toxicity of the prepara- 
tion very considerably. Xeufeld and DokP and Rosenow- obtained 
toxic substances from pneumococci, the former by extraction of the 
organisms in 0.1 per cent lecithin in physiological salt solution, the 
latter by simply autolysis, which induced symptoms in guinea-pigs 
suggesting acute anaphylaxis. Cole^ has repeated these experiments 
with results that were irregular; thus, of 213 guinea-pigs injected with 
extracts of pneumococci in salt solution, S died acutely with symptoms 
resembling acute anaphylactic shock, S3 died within twelve hours, the 
remainder were negative. Cole concludes that extracts of pneumococci 
in salt solution may be toxic, but not uniformly so. The exact con- 
ditions under which these solutions become toxic are unknown. Solu- 
tions of pneumococci dissolved in dilute solutions of bile salts were 
found to be very constantly toxic. ^ The intravenous injection of these 
solutions into rabbits and guinea-pigs elicits symptoms resembling 
closely those of acute anaphylaxis. Many of the animals die soon after 
inoculation. Sogen'' also has found that autolysates of pneumococcus 
cultures virulent for mice will cause circulatory changes and disturb- 
ances of heart rhythm when injected into rabbits. 
Hemotoxin.—HecentW Cole'' has shown that solutions obtained by 
dissolving pneumococci in dilute solutions of bile salts, or by tritura- 
tion, are hemolytic for rabbit, guinea-pig, sheep and human red 
blood cells, and that their activity is inhibited by minute amounts of 
cholesterin. The injection of these solutions in gradually increasing 
amounts leads to an inhibition of their action; in other words, this 
"hemolytic endotoxin" appears to act as an antigen. 
Pathogenesis.— //?/w?fl?2.— At least 90 per cent of all cases of lobar 
pneumonia, one of the most prevalent and fatal of human diseases, 
is caused by the pneumococcus. Thus, of 529 clinical cases of acute 
lobar pneumonia, 454 were associated with pneumococcus.^ This dis- 
ease is by no means the only one in which the organism is an etiolog- 
ical factor. Many bronchopneumonias which follow acute infections, 
as typhoid, diphtheria, so-called "aspiration pneumonia," are also of 
pneumococcic causation. Pleurisy, a frequent complication of both 
types of pneumonia, is cjuite commonly a pneumococcus infection, and 
a majority of sporadic cases of meningitis, particularly in chiklren, are 
' Berl. klin. Wchnschr., 1911, 48, 1069. 
2 .Jour. Iiifec. Dis., 1911, 9, 190. 
•1 .Jour. Exp. Med., 1912, 16, 644. 
•• Casagrandi (quoted by Pribram: Kolle and Wassermann Handb., 2 ed., 1913, 2, 
1350) states that normal rabbit blood contains antihemolysins. 
6 Tokoku Jour. Exp. Med., 1920, 1, 287. 
« Jour. Exp. Med., 1914, 20, .346. 
' Avery, Chickering, Cole and Dochez: Monograph 7, Rockefeller Institute, October, 
16, 1917. 
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