TABLE OF CONTENTS. 
Introduction — - 
I. Control experiments . . 
^-The action of normal horse serum upon normal guinea pigs 
4"The action of antitoxic horse serum upon normal guinea pigs 
4<[I. Horse serum is poisonous to a “treated” or “used” guinea pig 
The symptoms caused b} T the injection of horse serum into a susceptible 
guinea pig. 
The poisonous action of horse serum acts upon the respiratory center. . 
[ 'TIL The toxic action bears no relation to diphtheria 
The poison is not toxon 
4 Guinea pigs can not be rendered susceptible with previous infections with 
the B. diphtheiise 
^"Diphtheria toxine can not render guinea pigs susceptible 
Diphtheria antitoxin pla}’s no role in this action 
IV. The toxic principle 
Is the poison specific? 
Are other blood serums equally toxic? 
The relation of hemolysis .. 
The relation of precipitin to the toxic action 
The effect of heat upon the toxicity of horse serum 
L - — The toxic principle in horse serum is filterable through porcelain 
1 frying does not injure the toxic principle 
The toxic principle can not be separated by precipitation and dialysis. . . 
The effect of various chemical substances upon the toxic principle of 
horse serum 
The influence of antiseptics 
The effect of old horse serum upon susceptible guinea pigs 
'The effect of X rays upon the toxic principle 
V. The influence of time 
— The time necessary to render a guinea pig susceptible 
i — - The guinea pig remains susceptible a very long time 
VI. Dosage as a factor 
The minimal amount of horse serum necessary to render a guinea pig 
susceptible 
The minimal amount of horse serum necessary to poison a susceptible 
guinea pig 
The influence of large quantities in rendering guinea pigs susceptible. 
VII. The sensitizing substance. 
Guinea pigs may be sensitized with precipitated and dialyzed serum 
Drying does not injure the sensitizing substance 
Small quantities of horse serum may render guinea pigs more susceptible 
than large quantities 
The sensitizing substance is not free in the blood serum 
The effect of heat upon the sensitizing substance 
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