42 
sticking to each other. As it is probable that some of these bottles 
ayUI be kept for years, this may be an important detail. The neck of 
the bottle is carefully dried and then quickh" dipped into melted paraffin 
Avith a high melting point so as to seal the joint completely and preA^ent 
evaporation or contamination. 
Each bottle is labeled and stored in a special ice box kept at a con- 
stant temperature of 5° C. 
It Avill be seen that according to this method the toxine is kept in 
absolute darkness, free from contact Avith the oxygen of the air, and 
at an equable and Ioaa' temperature. By the use of the ordinary bac- 
teriological precautions the addition of a preseixatAe as toluol and 
similar substances is rendered unnecessary. 
' TESTING THE TOXINE. 
It is first necessaiy to determine the minimal lethal dose of the tox- 
ine with approximate accuracy. Weak poisons are discarded. A fresh 
toxine requiring more than 0.01 c. c. to kill a 250-gram guinea pig is 
too Aveak for the purposes of this special AA'ork. 
If the preliminary tests show that the poison has the required tox- 
icitAN its minimal lethal dose must then be accurately determined. 
This may require a number of animals. 
After the absolute toxicitA^ of the poison has l)een determined it is 
necessary to establish the L-fi and the L® doses. An illustration of 
how these doses aie obtained folloAvs. These results are taken from 
our records. 
Tests to determine the Ld~ dose of toxine Xo. 7. 
Ke.sult. - * 
1 immunity unit +0.19 c. c. toxine 
Invariably causes late paralysis, neA’er 
■ 
acute death. 
1 immunity unit — .20 c. c. toxine 
Sometimes causes late paralysis and 
! sometimes acute death. 
1 immunity unit + .21 c. c. toxine 
Always causes acute death about the 
fourth day. 
1 immunity unit + .22 c. c. toxine 
Always causes acute death, usually on 
the second or third day. 
The L-j- dose of this toxine is, therefore, just 0.21 c. c. 
