414 



PHYSIOLOGY 



CHAP. 



muscles of the upper intercostal spaces work simultaneously, and 

 the entire thorax is slightly elevated by the contraction of the 

 scaleni. It follows that both the external intercostals and the 

 intercartilaginous muscles are active in the inspiratory position, 

 although they have an opposite course (gJi^>g'h f , kl^>k'l'). This 

 view of Hamberger's was better illustrated at a later time by 

 Hutchinson (1852). 



It is supported as regards the inspiratory action of the external 

 intercostals by direct observations on the living. These muscles 

 have been observed on animals to become tense, and to harden and 

 thicken during inspiration, while during expiration they relax and 

 flatten (Antonio Marcacci, 1843 ; Duchenne, 1866 ; Eosenthal, 



1882). When in the dog 

 or cat a section of the in- 

 ternal intercostal muscle is 

 exposed by care fully cut ting 

 away the external intercostal 

 that covers it, so that both 

 intercostal muscles, the ex- 

 ternal and internal of one 

 or two adjacent intercostal 

 spaces, can be simultane- 

 ously observed, an alternate 

 contraction of their fibres 

 can be detected those of 

 the external intercostals 

 being active during in- 

 spiration, and those of the 

 internal intercostals during 

 expiration (Ant. Marcacci). 

 At a later time this was 

 confirmed by graphic records, 

 which showed that the 

 internal interosseal intercostals contract alternately with the 

 diaphragm, and therefore have an expiratory action (Newell-Martin 

 and Hartwell, 1879). 



The experiments with localised electrical stimulation, which 

 proved to Duchenne and others that there was always a narrowing 

 of the intercostal space and elevation of the lower above the upper 

 rib, either when the external intercostals alone are stimulated, or 

 when the internal are excited as well, does not contradict the 

 above facts, since normally, in inspiration, all the external inter- 

 costals contract synergically, the thorax being lifted and supported 

 by the scaleni, which must necessarily cause distension of the 

 intercostal spaces. 



The function of the intercartilaginous muscles, again, has been 

 experimentally confirmed. K. du Bois-Keymond and P. Masoin 



FIG. 180. Schema to demonstrate that the function 

 of the internal intercartilaginous intercostals is 

 identical with that of the external interosseous 

 intercostals. 



