American journal of physiology . ed by one or more stimuli{e. g., carbon dioxid or intermediate acids). Even writers who prop-erly insist on attention to alveolar rather than total ventilation do notalways seem to take into account the fact that alveolar ventilation itselfis the result of the cooperation of several factors each of which mayshow very different degrees of development or of irritability in differ-ent individuals. There seems to be sufficient indication of the exis-tence of three variables in this mechanism, namely: 1. Factors determining the respiratory rate. 2. Factors determini
American journal of physiology . ed by one or more stimuli{e. g., carbon dioxid or intermediate acids). Even writers who prop-erly insist on attention to alveolar rather than total ventilation do notalways seem to take into account the fact that alveolar ventilation itselfis the result of the cooperation of several factors each of which mayshow very different degrees of development or of irritability in differ-ent individuals. There seems to be sufficient indication of the exis-tence of three variables in this mechanism, namely: 1. Factors determining the respiratory rate. 2. Factors determining the amount of inspiratory effort. 3. Factors determining the amount of expiratory effort. The very existence of these possibilities makes it important that instudies upon the respiratory centre — involving, as they so largely do,experiments with dyspneic conditions—the character of the normal re-sponse of the subject to such conditions should be known beforehand. 382 Theodore Hough. IV. The Minute Volumes of Inspired Fig. 6 gives the platted curves of minute volumes from seven sub-jects. These may be regarded as representing the range of variationseen in my experiments. The curve T. H. is typical of that given by8 subjects; J. B. S., 6 subjects; R. R. D., 4 subjects; and J. O. C.(and J. 0. M.), 3 subjects. The curves of J. B. L. and C. L. W. do not coincide closely with anyothers. These curves present dif-ferences in the volume of airbreathed during the sameminute of the experiment, inthe rate of increase in succes-sive minutes, and in the formof the curve. We may beginwith a discussion of the firsttwo of these points of differ-ence. There can be no doubtFigure 6. — Curves of minute volumes from 7 that these are partly due tOsubjects of these experiments. The numbers ,i r .li. i . ., r. .u • •.• 1 .u . 1 the use of the same volume m parentheses after the mitials are the total number of subjects giving curves of the same of ^.ir by SUbjectS of different type
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