75 



so as to form an elastic cushion, compressible in 

 any direction, but always ready to fill out again. 

 On this cushion the front ribs rest themselves, and 

 not only are the movements thus made more 

 smoothly, but achial aid is given to the ensuing 

 gathering hy the expansion of the air compressed in 

 the lungs during the spring. 



We shall have occasion to go thoroughly into the 

 discussion of that action of the anterior and pos- 

 terior parts of the lungs, which in the higher ani- 

 mals belongs to the anterior and posterior portions 

 of the central S curve of the body, and shall post- 

 pone further consideration of the subject to that 

 time. We may, however, observe that the form 

 which would give the greatest capacity to that pai-t 

 of the body in which the lungs are situated, is 

 that of the full gathered superimposition of ticists 

 (§ 71). In this the ribs are raised toward the head 

 iDy their ground ends as much as possible, while 

 the point where the two turns meet is also raised 

 outward by the depression of their spinal ends. 



