H 



QUATERCENTENARY STUDIES IN PATHOLOGY 



shown that under these conditions the supply of oxygen is sufficient to 

 satisfy an organism so exigeant in this direction as B. diphtheriae. 



Appearance and Age of the Culture. — The cultures vary greatly in the 

 appearances they present. In certain cases the growth begins as minute 

 flocculi in the bouillon, the surrounding fluid remaining clear. Other 

 cultures show an almost uniform turbidity. To certain of the flasks 

 cocoa butter or butter was added, and in these good stalactite formation 

 was observed. No connection between the type of growth and the 

 toxicity could be determined. The culture, as it increases in age, 

 becomes very alkaline, and in two months there is usually a large deposit 

 containing bacterial debris and masses of crystals of triple phosphates. 



One change is of considerable significance in relation to toxin 

 formation. A platinum loopful from a culture a few days old, planted 

 on an agar plate, gives an abundant growth, whereas, from a flask two 

 months old, little or no growth may be obtained unless a larger quantity 

 of material be employed for inoculation. In the two months' old culture, 

 almost all the bacilli present have lost the usual morphological characters 

 of the plague bacillus, the deposit in the flask consisting almost entirely 

 of bizarre involution forms or mere detritus. 



The Period of Maximum Toxicity. — Some preliminary tests were made 

 on the toxicity of the filtrates from cultures lO days and two months old 

 in bouillon of the same brew. Such a test shown in Tables III. and IV. 

 indicates that at lo days, if toxin is present, its concentration is much 

 less than at two months. 



TABLE III.— Toxin 7. 



Filtrate from 10 day's growth on Neutral Broth. 

 Test on Mice 15-20 grammes weight 

 Subcutaneous injection. 



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