DIPHTHERIA TOXIN AND ANTITOXIN 



485 



the above operations and in the finished condition, the toxin 

 should be stored in a cool place. 



It has been our experience in evaluating the strength of the 

 diphtheria toxin for injection purposes, that the L + dose method 

 (according to the Hygienic Laboratory) furnishes a more reli- 

 able index than determination of the minimum fatal dose. Al- 

 though the theoretical relationship may not exactly hold, the L + 

 dose for all practical purposes may be considered as 100 M. F. D. 



III. GENERAL OBSERVATIONS 



It will be readily conceded that we can best judge the value of 

 what has been presented from the actual results of practical 

 application. Data obtained during the past year in the pro- 

 duction of several thousand gallons of diphtheria toxin by the 

 general method indicated, are summarized below. 



PRODUCTION RESULTS 



Diphtheria toxin 



Percentage of total toxin having L dose 



As may be noted, practically 90 per cent of the toxin produced 

 was of usable strength, — L+ dose = 0.50 cc. or less. Of this, 

 more than 78 per cent was high strength, having an L + dose of 

 0.33 cc. or less, and 43 per cent was so strong that one L + dose 

 was 0.25 cc. or less. In view of the fact that only about 10 per 

 cent of the large amount of toxin produced failed to reach a de- 

 sirable strength, the procedure and medium recommended above 

 can be considered as meeting practical requirements. 



It is interesting to note, in connection with the production of 

 diphtheria toxin, that no definite seasonal or weekly variation, 

 as mentioned by MacConkey (1912) was observed. Occasion- 

 ally, one or two bottles of a large lot would show an inferior or 

 weak toxin, in spite of the fact that, as far as could be determined, 

 the contents of all bottles after filtration should have been identical. 



