MUSCLES OF THE PARIETES OF THE ABDOMEN. 397 



of the twelfth rib ; with the upper edge of this ligament the 

 diaphragm is connected; and with the lower, the psoas mag- 

 nus muscle, and the quadratus lumborum. At the margin of 

 the other ribs, the diaphragm is connected with the transver- 

 salis abdominis. 



Use. In consequence of the muscular fibres of the diaphragm 

 passing in a curved direction from the circumference of the 

 thorax to the cordiform tendon; and of those fibres forming a 

 body concave below and convex above, their contraction at 

 the same moment enlarges the cavity of the thorax, and has a 

 tendency to diminish that of the abdomen, which latter is pre- 

 vented by the yielding of the abdominal muscles. In easy res- 

 piration, its contractions and relaxations produce alternately 

 the actions of inspiration and of expiration. Its descent, also, 

 assists in the expulsion of faecal and other matters from the 

 abdomen. By the experiments of Bourdon,* it appears that it 

 only acts a secondary part in the latter, that its functions are 

 limited to inspiration and the associated actions; but that in 

 regard to its power of assisting in the expulsion of the contents 

 of the abdomen, all that it does is first of all to fill the lungs 

 with air, and then the closure of the glottis prevents the air from 

 being expelled from the lungs. Common observation in partu- 

 rition shows us, that the expulsive effort of the abdominal mus- 

 cles does not take place when inspiration is going on, for the 

 former would prevent the latter; but the moment that expira- 

 tion begins, it is arrested by the firm closure of the glottis, and 

 then the abdominal muscles contract advantageously. 



The Quadratus Lumborum, 



Is an oblong muscle, arising from the crista of the ilium, at 

 the side of the lumbar vertebras, by a tendinous and fleshy ori- 

 gin of three inches in length. It is inserted into the transverse 

 process of each of the lumbar vertebrae and of the last of the 

 back by a short tendinous slip: it is also inserted into the low- 

 er edge of the last rib near its head, beneath the ligamentum 

 arcuatum. 



It bends the loins to one side, and draws down the last rib. 



* Recherches sur la Respiration et la Circulation. Paris, 1820. 

 VOL. I. 34 



