In order to estimate the value of any method of artificial respiration it is necessary to bear in mind certain general principles and to determine with some approach to accuracy certain statistics. The most important of the principles concerned is the elasticity of the lungs and thorax, by virtue of which alterations in volume caused by distortion of shape under the influence of an external force are followed, on removal of the distorting force, by a return to the original volume. It is by virtue of this principle that expiration is ordinarily effected, the distorting force usually acting so as to increase the capacity of the thorax by raising the ribs and depressing the diaphragm; on its removal these parts return to their original position. But, artificially, the distorting force can be made to act in an opposite manner, viz., by diminishing the capacity of the thorax and thereby forcing