PHYSIOLOGICAL ACTION OF NITROBENZENE VAPOR ON ANIMALS 427 
5. That nitrobenzene is not necessarily converted in the body into 
anilin, hydrocyanic acid, or any other substance before it exerts a toxic 
action. 
6. That nitrobenzene forms methemoglobin in the blood. 
The following points, altho suggested, have not been satisfactorily 
explained: 
1. The exact seat of action of nitrobenzene. 
2. The cause of the latent period. 
3. The reasons for the variability of the size of the lethal dose. 
4. The reasons for the inconstancy of the symptoms of poisoning. 
5. The significance of the various types of symptoms observed. 
APPARATUS AND TECHNIQUE OF PRESENT EXPERIMENTS 
APPARATUS 
The apparatus used in these experiments was designed after a con- 
siderable period of experimentation with various devices; and, since it 
is such as may be used for investigating the physiological actions of a great 
many different gases, the principal parts are here described more or less 
in detail. 
The apparatus consists primarily of a fumigation chamber, with accessory 
devices for saturating, dehydrating, and aerating this chamber. In 
addition apparatus was provided for determining the purity of the nitro- 
benzene used, such as devices for ascertaining the boiling point, the freez- 
ing point, and so on; and apparatus for determining approximately the 
amount of nitrobenzene vapor to a cubic foot of space within the fumigation 
chamber. 
The fumigation chamber consists of a galvanized iron tank 60 inches 
long, 40 inches wide, and 30 inches deep. These dimensions were chosen 
so that the tank could be readily carried thru doorways. The chamber 
has a capacity of 43.75 cubic feet. A metal fossa, $ inch wide and # inch 
deep, was constructed around the outer top edge, to receive the rim of 
the cover. When it was desirable to seal the tank, the cover was piaced 
on and melted paraffin was poured into the fossa, thus rendering the 
tank air-tight. The cover is provided with two glass windows, one 8 x 10 
inches and the other 12x 18 inches. The larger window is removable, 
and fits into a slot in such a way that it can be sealed and unsealed readily ; 
