404 Journal of Agricultural Research voi. vm, No. n 
Lugol’s solution, of a rich port-wine color, for 2 minutes, then again, with¬ 
out rinsing, put in 95 per cent alcohol for 15 minutes to decolorize. 
Oxygen requirements. —In determining oxygen requirements, cul¬ 
tures are inoculated into a deep tube of 1 per cent glucose agar after 
thorough boiling to drive off oxygen. The tubes are cooled as rapidly 
as possible after inoculation. The presence or absence of growth at 
the surface and in the depth of the tube is noted. 
Animae inoculation. —Rabbits and guinea pigs were used for testing 
the pathogenesis of the organisms. Neither B . vulgatus nor B. mesen - 
tericus was found to be pathogenic for guinea pigs. B. vulgatus was not 
found to be pathogenic for rabbits. Inoculations were made subcuta¬ 
neously. 
Thermae death point. —One will be impressed by the great discrep¬ 
ancy in the results of the experiments of different investigators to deter¬ 
mine the amount of heat required to kill organisms or their spores. 
Rosenau (12, p. 683), in a study of the temperature required to kill the 
tubercle bacillus, gives a table showing the results gained by 32 inves¬ 
tigators, including his own. The results of only 8 of these investigators 
agree. Discrepancies equally as great occur in the results given for 
organisms other than the tubercle bacillus, as will be found on considera¬ 
tion of the literature. Such lack of agreement in results may be only 
apparent. It is not at all unlikely that the temperature at which organ¬ 
isms or their spores are killed varies under different conditions more 
than is generally supposed. Among the factors which may operate to 
cause such a variation in results may be mentioned the age of the cul¬ 
ture, the kind of medium used, including the amount of moisture present, 
the length of time of incubation, the amount of culture heated, etc. If 
the results secured are to be of the greatest practical value, an attempt 
should be made to determine under what conditions organisms or their 
spores withstanding the greatest amount of heat are produced and 
exist. In. the attempts to determine the thermal death point of B. 
vulgatus and B. mesentericus two methods were used. In one a suspen¬ 
sion of spores was prepared in test tubes of bouillon loosely plugged with 
cotton (13). The tubes were placed in an open vessel of water of the 
temperature desired, and, after time was allowed for the tubes to acquire 
the temperature of the water bath, the heating was continued for the 
desired length of time at the desired temperature. The tubes were then 
removed from the water bath and cooled rapidly. In the other method, 
tubes of soft glass of about inch internal diameter were drawn to a 
capillary tube at one end and in the middle, leaving two bulblike expan¬ 
sions. These were sealed in the flame at one end after drawing up the 
spore suspension. Owing to the fact that one capillary end was left 
open during the heating, this method can not be used for the boiling 
temperature, since some of the suspension is forced out, contaminating 
the water bath and consequently the outside of the other tubes. By 
