470 RESPIRATION. 



cartilage, to the lower ends of the two last true, and of all 

 the false ribs, to the inner aspect of the last rib, and through 

 two strong muscular prolongations (pillars) to the bodies of 

 the lumbar vertebrae. It is not a straight partition, but 

 bulges forwards into the thorax, its anterior aspect being 

 markedly convex, while the posterior is correspondingly 

 concave. The contraction of the muscle necessarily approaches 

 it to the flattened form, increasing the antero-posterior 

 dimensions of the thorax, and diminishing those of the 

 abdomen. The viscera of the abdomen are accordingly 

 pushed backwards, and cause a bulging of the abdominal walls, 

 from which this process has received the name of abdominal 

 respiration, in contradistinction to the lateral dilatation of 

 the thorax, or thoracic respiration. In the ox, the diaphragm 

 is attached upon the inner aspects of the two last ribs, so 

 that the last intercostal space is not related to lung or pleura 

 in those animals. The diaphragm, too, in their case, projects 

 far into the chest, since the hand introduced into the rumen 

 can readily feel the sixth rib. 



When, by these means, the thorax is dilated, the lung 

 which occupies the whole of its interior, with the exception 

 of the mediastinum, and the surface of which is constantly in 

 contact with its parietes, must necessarily increase in size. 

 Air accordingly rushes in to fill up the cavities of the air 

 cells, and prevent the occurrence of a vacuum. Coincident 

 with the dilatation of the thorax, the glottis, and the anterior 

 opening of the nostrils, have their capacity increased, so that 

 we have a simultaneous and regular or rythmic action of all 

 those parts, to insure a constant and free supply of air in the 

 pulmonary cells. The dilatation of the anterior nares is well 

 marked in solipedes, since the false nostrils of these animals 

 give this part great mobility, and these are fully distended 

 during laboured breathing. The opening of the glottis is 



