48 
Tests to determine the L'* dose of toxine Xo. 7. 
1 immunity unit — 0.14 c. c. toxine 
1 immunity unit -r -15 c. c. toxine 
1 immunity unit 4- -16 c. c. toxine 
1 immunity unit -p .17 c. c. toxine 
1 immunity unit — .18 c. c. toxine 
1 immunity unit — .19 c. c. toxine 
Result at autopsy forty-eight hours after inocu- 
lation. 
Xo visible reaction. 
Xo visible reaction. 
Slightest possible congestion about car- 
bon particles, or no reaction. 
Apparent reaction at site of inoculation. 
Injection and edema at site. 
I Injection and edema at site. 
The L" dose of this toxine, therefore, is 0.16 c. c. 
These figures are actual results obtained with our toxine Xo. 7. 
If the interval between the L+ and the L*’ dose is greater than 
IoXjMLD, the toxine contains too great a proportion of toxones, etc., < 
and should not be used for testing the strength of antitoxin. If it were 
possible to obtain ideally pure toxines in which the interval between 
the LH- and the L® dose was only one minimal lethal dose, our prob- 
lem would be simplified. Unfortunateh" such a poison has onh^ once 
been demonstrated. However, by these preliminar}^ tests upon a 
number of poisons we select the most suitable for the purposes of this 
special work. 
Having selected a suitable poison, it is now laid aside to season. 
For this purpose the toxine should be kept in bulk, so that the process 
will be uniform throughout the mixture.^ If it is kept in diflused 
light at. room temperature, the changes will take place quicker than if 
kept in the ice box. At intervals of about a month the toxine is tested 
in order to determine the rate of change. These examinations will 
disclose' the fact that the toxicity gradually diminishes and the L+ 
dose increases. These alterations take place progressively until the 
poison arrives at a stage of equilibrium. Here it ma}^ remain for a 
long time. A short time before this stage of equilibrium is reached it 
is best to divide the toxine into small bottles, excluding the air, in order 
to guard against loss by accident or contamination, and store the entire 
lot in a cold place protected from light. 
The toxine can not be depended upon for the purpose of testing the 
antitoxin until this stage of equilibrium is reached. After a varying 
length of time the toxine will again show change in toxicity, and when 
this second period of change sets in tl\e toxine should be discarded as 
no longer serviceable for the purposes of these tests. 
As soon as the toxine has reached its stage of stabilit}" or equilib- 
rium, that is, when the test dose remains constant, it is necessaiw to 
determine this test dose (L-b) with the greatest possible accuracy. 
The well-standardized toxines used in this laboratory are tested 
