RESPIRATORY APPARATUS. 



119 



its points of insertion, extending into the thoracic cavity in the 

 shape of a cone the apex of which reaches in the various ani- 

 mals, somewhat beyond the middle of the 7th or 8th rib. At 

 expiration the diaphragm lies with its muscular portion directly 

 against the lateral chest wall, the tendinous portion then forming 

 the partition. With the beginning contraction of the diaphragm 

 at inspiration the arch becomes flattened in that the organ is 

 drawn away from the inner wall of the chest. The space left 

 by the receding diaphragm is immediately occupied by the sharp 

 borders of the lungs which then lie close to the points of insertion 

 of the diaphragm. At the acme of inspiration the rounded, cone- 

 like form of the diaphragm becomes more pointed and its base 

 and apex approach each other, the ribs having been drawn for- 

 ward. By this drawing forward of the ribs the transverse diam- 

 eter of the thorax is increased and the base of the cone-like dia- 

 phragm broadened. (See page 92.) 



Fig. 33. 

 — — Dorsal and Ventral boundaries of field of pulmonary percussion. — - — 

 attachment of diaphragm. — - - — Curvature of diaphragm in median plar 

 Anterior boundaries of stomach divisions. H. Heart. P. Paunch. 



Accordingly, the lateral border of the lung is continually 

 moving backward and forward, traveling a distance in the larger 

 animals of 1-3 hands breadth, and in the smaller ones from ^ to 1 

 hands breadth. On an average the posterior border of the lung 



