The experimental study of respiratory reserve reported here is a continuation of similar work done a year ago. At that time, the efficiency of the mechanical factors of respiration received most attention. This study deals more particularly with the effects produced on the respiratory reserve by lessened mechanical efficiency. It represents an attempt to discover the point at which reserve is lost, at which respiration as a function is inadequate, and at which circulatory aid is required so that the animal can maintain a comfortable existence.
From among the group of animals under observation, an especially intelligent dog was chosen and was taught to lie quietly while wearing the usual mask employed in taking basal metabolic readings. This training was necessary before the undertaking of any of the operations that were employed and that were designed to lessen mechanical efficiency and to decrease vital capacity. The dog was vigorous and