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Rh it over the spirit-flame, not only on account of the risk of distracting the subject’s attention with a warm tube, but on account of the danger of heating the inside of the odorous cylinder.

Since the source of the odorous vapor is connected with the subject’s nose by a tube of known length, the diffusion of the matter is, outside of the body, obviously under complete control.

The subject's breathing is, indeed, a seriously variable element, but its variation is by no means the greatest practical drawback to the method. Sniffing must, of course, be watched for and peremptorily forbidden, The mere expansion of the nostrils does not increase the intensity of the odor as it does under ordinary circumstances, but rather decreases it, since the field of smell is artificially limited, and the widening of the entrance to the nose simply increases the amount of air which dilutes the odorous gas. Under ordinary circumstances, as we have seen, the more rapidly one breathes, the stronger the odor one will get. If one uses the olfactometer, this is not true. Since the diffusion-rate within the cylinder is constant, increased rapidity of breathing will increase the degree in which the odorous particles are diluted with air on their entrance to the nasal passages. Thus, the more slowly one breathes, within a certain limit, the stronger the smell one will get. 'The air must be drawn in with enough force to carry part of the current above the lower turbinal bone. If the air simply takes the straight path to the choana along the floor of the nasal cavity under the lower turbinal bone, there will be no smeli. Zwaardemaker believes that each subject with a little practice will discover for himself the best rate of breathing for obtaining the strongest smell from a given stimulus, so that, in a manner, the breathing rate will be self-regulating. Our own experimental results seem to bear out this conclusion. In Section 1 of Chapter III, each subject’s mode of breathing is noted, but its peculiarities can scarcely be traced in the numerical results. The inability of most of the subjects to arrive at difference-determinations with one inspiration must, of course, have aggravated the adhesion-error. Henry regulates the breathing of his subjects by putting about the chest a belt which allows only a certain expansion, Such an appliance must, however, have the effect of distracting the subject's attention and making the breathing unnatural. Following Zwaardemaker's example, we did not even stop the nostril not in use, The inhaling-tube was thrust into the forward half of the nostril to the depth of half a centimetre.