OF RESPIRATION. 87 



This holds good chiefly with the six pairs of true ribs 

 below the first pair, each of which is more moveablo 

 than the one above in proportion to the greater length 

 both of its own body and of its cartilaginous appendix. 

 The cartilages are united by a kind of amphiarthrosis 

 to the margin of the sternum on each side. (B) 



144. Between the edges of the ribs lie two strata of 

 intercostal muscles, differing in the direction of their 

 fibres, but conspiring to produce the same motion. 



At the base of the thorax, the diaphragm* is sub- 

 tended in the form of an arch. It is a considerable 

 muscle, and, in the words of Haller, next in importance 

 to the heart. Its utility in the mechanical part of res- 

 piration w as long since shewn, by the excellent expe- 

 riments of Galen f upon living animals, to depend 

 chiefly on the phrenic nerve. 



Its antagonists are the abdominal muscles, especially 

 the two oblique and the transverse, 



145. The thorax thus constituted, is, after birth, 

 dilated by inspiration and subsequently reduced to a 

 smaller capacity by expiration. 



During the former act, the thorax is enlarged late- 



Tubing. 1769. 4to. Theod. Fr. Trcndelcnburg, Jim. Desterni costarumque in. 

 n-jiirrttiunt veru gemiinaque mot us ratione. Getting. 1779. 4tO. Bordenave 

 and Sabatier, Mem. tie VAcad. des Scienc. de Paris. 1778. 



* Haller, Icon. Jiiat. fascic. 1, Tab. 1. 



B. S. Albimis, Tali, mnsatlor. Tab. xiv. fig. 5, 6, 7. 



J. G. Riidcrer, De nrcubits (fiiilineis muscul. progr. 1. Getting. 17CO. 4tO. 



Santorini, Tab. Posth. x. fig. '1. 



t DC .liKitomicis Adtiiutistrntwiiilius. L. viii. cap. 8. The whole book is 

 full of experiments on respiration. 



t Ephr. Kri'iger, De itervo pkrenico. Lips. 1759.; reprinted in SandUwl's 

 Thesaurus. Tom. iii. 



Walter, Tab. ncn-or, thorac. et abdominis. Tab. 1. fig. 1. n. I, 



