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produced b}" the first injection come in contact without delay; their 
union is rapid; the whole charge of the poisonous substance is quickly 
set free and the toxic symptoms are sudden and severe. 
Besredka and Steinhardt" had, as a working hypothesis, the follow- 
ing: The sensitized guinea pig which appears in good health has, in 
spite of its apparent well-being, perhaps a latent lesion of the brain. 
A second injection of serum, made into the peritoneal cavity twelve 
daj^s later, is able to awaken this nervous lesion, resulting in grave 
symptoms or even death. 
In view of these theoretical considerations it is important to make 
further studies upon the sensitizing substance in horse serum and 
other proteid substances. 
The following experiments show that the filtrate from horse serum 
after precipitation with ammonium sulphate renders guinea pigs sen- 
sitive. The filtrate contains most of the serum albumen and very little 
of the globulins. It is exceeding!}^ weak in antitoxic strength. 
G. P. No. 400. Six c. c. antitoxic horse serum (Natl. VIII., 18), intraperitoneally. 
Marked symptoms. ■« 
[Previous treatment: 38 days prior, 5 c. c. filtrate of antitoxic serum, precipi- 
tated (NYBH). Subcutaneously.] 
This filtrate was kindly furnished us by Dr. W. H. Park from some 
antidiphtheric serum undergoing the Gibson process of refining. 
The following experiments show that formaldeli3^d does not destroy 
the sensitizing property of horse serum : 
G. P. No. 390 W. Six c. c. normal horse (roan) serum, intraperitoneally. Severe 
symptoms. 
[Previous treatment: 47 days prior, 6 c. c. antitoxic horse serum (Natl. XVIII) + 
1 per cent formalin, 23 hours exposure. Subcutaneously.] ! 
G. P. No. 500 W. Six c. c. normal horse (roan) serum, intraperitoneally. Very 
severe symptoms. 
[Previous treatment: 29 days prior, 3 c. c. normal horse (roan) serum-[-5 per 
cent formalin, 4 hours 30 minutes exposuure. Subcutaneously.] I 
The results with formaldehyd have a special significance in view of 
the fact that this active reducing agent is capable of destroying the | 
poisonous properties of tetanus and diphtheria toxines. ! 
AVe have shown before that the sensitizing and poisonous principles | 
in horse serum are not dialj'zable through parchment paper. From • 
the following limited experiments it would seem that the sensitizing [ 
principle is not dialyzable through a collodion sac when placed in the ;| 
peritoneal cavity of the animal. i 
G. P. No. B. Six c. c. normal horse (No. 15) serum, subcutaneously. No symptoms. ;| 
[Previous treatment: 32 days prior, collodion sac containing about 3 c. c. normal |J 
horse (No. 15) serum placed in peritoneal cavity.] , 
« Besredka, A., and Steinhardt, Edna: De I’anaphylaxie et de I’anti-anaphylaxie '' 
.vis-a-ws du serum de cheval. Ann. de I’lnst. Pasteur, Yol. 21, No. 2, Feb. 25, 1907, , j 
pp. 117-127. 
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