179 



2. The domes of the diaphragm reach as high in front as the '2nd. 

 or 3rd. rib. Thus the thorax is very small and mostly consists of a 

 long backwardly directed space between the diaphragm and the dorsal 

 parts of the ribs. It is thus obvious that costal movements can have 

 little to do with respiration in this animal. 



3. Each lung in consequence has its diameter from apex to base 

 very markedly diminished. On the other hand the diaphragmatic 

 area is exceedingly large and the lung substance between diaphragm 

 and costovertebral surface much extended. 



Fig. 2. Transverse section of wall of large intrapulmonary bronchus from lung 

 of Elephas. magnified 47 diameters, a. Mucous membrane, b. Inner elastic tissue, 

 c. Muscular coat. d. Outer elastic tissue coat. Note absence of cartilaginous tissue. 



Note that contrary to Moerison Watson's opinion there is a 

 definite and ver}- extensive diaphragmatic surface of the lung. 



The small bulk of lung tissue compared with the relatively large 

 diaphragmatic area and the disposition of the diaphragm in elephants, 

 emphasise the importance, in these animals, of diaphragmatic res- 

 piration. 



When one considers the long and comparatively narrow tubes 

 (in the proboscis) through which air reaches the lungs in these creatures, 



