NEW VIEW OF THE MECHANISM OF RESPIRATION 



283 



column, forbid their acting otherwise. In making this statement I am fully aware of the jointed parallel bar models 

 actuated by obhque elastic bands employed to demonstrate the contrary. The models do not, however, represent 

 the action of the interossei muscles accurately. 



When muscles run obliquely and cross each other, the rule is that they act synchronously and produce a 

 common result ; in other words, the two sets of muscles do not act against each other, the one set pulhng up and 

 the other pulhng down and the converse. 



I will have occasion to return to the respiratory muscles presently, but it may facihtate matters if, before doing 



Fli:. 47. 



Fig. 47. — A. Original ]ihotograpli of the cavities of the thorax and abdomen as seen anteriorly or in front. Shows the ribs, 

 position of the diaphragm, the great blood-vessels, intercostal and other muscles, a, Backbone with ribs attached, also intercostal 

 muscles ; h, V, right and left sides of diajihragm ; c, psoas magnus and parvus muscles ; d, quadratus lumborum ; e, d, iliacus muscles ; 

 /, transversalis abdominis muscle (the Author). 



B. Original photograph of the cavities of the thorax and abdomen as seen posteriorly or from behind. Shows rounded heads of 

 arms and thigh bones so essential in locomotion, the ribs and intercostal muscles, rectus muscles, and the position of the diaphragm. 

 g, Rounded head of right humerus or arm bone ; h, rounded head of left arm bone ; i, rounded head of right thigh bone ; j, rounded head 

 of left thigh bone. The arm and leg bones are provided with ball and socket or universal joints, and can be moved pendulum fashion 

 in any direction in walking and running, k, Sternum or breast-bone with sterni miiscles, also intercostal nmscles ; I, I,' right and left 

 halves of diaphragm ; m, the two recti-abdominal muscles separated by the linea alba ; n, n', the two transverse abdominal muscles 

 (the Author). 



so, I give illustrations of the thoracic and abdominal cavities separated by the diaphragm, and also the osseous 

 framework of the chest and abdomen. To these cavities and bones the respiratory muscular arrangements must 

 be ultimately referred (Fig. 47 A and B). 



At A and B of Fig. 47 sections of a frozen human cadaver are seen. In both cases the contents of the 

 thorax and abdomen have been removed. At A the cavities are seen from before and at B from behind. In both 

 figures the position and shape of the diaphragm [h h', I V) are correctly portrayed. The attachments of the diaphragm 

 are also indicated. At B, the recti abdominis covered by their sheath and separated by the linea alba are clearly 

 indicated. At n nf the transversales abdominis occur. Other details are given in the descriptions of the figures. 



The osseous framework of the chest and abdomen performs a not unimportant part in the great subject of respira- 

 tion. It acts as a protecting shield or covering, especially to the thorax, and furnishes origins and insertions to the 



