XII 



MECHANICS OF RESPIRATION 



411 



Since the direction of the fibres in the M. levatores costarum 

 and the M. intercostales externa (Figs. 177 and 178) coincide, it 

 is natural to regard these also as inspiratory muscles. 



The function of the intercostal muscles, external as well as 

 internal, has, however, been a subject of endless controversy, 

 beginning with the lively polemic between Haller and Hamberger, 

 and lasting into our own day. The most varying and opposite 

 points of view have found strong supporters. Setting aside the 

 opinion of Galen and Bartholin, who reckoned the external 

 intercostals to be expiratory, and the internals inspiratory ; and 

 the view of van Helmont, Arantius and others who denied any 



FIG. 177. Intercostal muscles of 5th and 6th spaces. (Allen Thomson.) A, Hide-view ; B, back- 

 view ; IV, 4th dorsal vertebra ; V, 5th rib and cartilage ; 1, 1, M. levatores costarum longi 

 et breves ; 2, 2, M. intercostales externa ; 3, 3, M. intercostales interni, as shown by 

 removal of externi in lower intercostal space. In A there are no external intercostals in 

 the intercartilaginous spaces ; in B there are no internal intercostals near the vertebral 

 column. 



active function whatever to the intercostal muscles, and regarded 

 them merely as the complement of the thoracic wall, as well as the 

 opposite view of Mayow, Magendie, Burdach, etc., who held both 

 externals and internals to be alternately inspiratory and expiratory 

 in function ; there remain four other aspects of the question, which 

 are defended with conflicting arguments by distinguished physio- 

 logists, and are set forth in modern text-books : 



(a) Both external and internal intercostal muscles are in- 

 spiratory (Borelli, Senac, Boerhaave, Winslow, Haller, Cuvier, 

 Duchenne). 



(b) Both kinds of muscles are expiratory (Vesalius, Diemer- 

 Brock, Sabatier, Beau and Maissiat, Longet). 



