248 THE MUSCLES. 



so that towards this point the phrenic centre is not enveloped by the 

 peripheral portion, and is in contact with the sublumbar region. 



Attachments. 1, To the bodies of the lumbar vertebrae by the tendons 

 of its two pillars, which tendons are confounded with the inferior common 

 vertebral ligament ; 2, By the external contour of its muscular portion, to 

 the superior face of the xiphoid appendage and the inner face of the last 

 twelve ribs, near their inferior extremities or cartilages. The digitations 

 forming the last insertions do not intercross, in Solipeds, with those of the 

 transverse muscle of the abdomen, being separated by an interval which is 

 wider behind than before. 



Relations. The anterior face of the diaphragm is covered by the pleura, 

 and responds, mediately, to the base of the lung. The posterior aspect, 

 covered by the peritoneum, is in contact with the greater part of the viscera 

 contained in the abdominal cavity the stomach, colon, spleen, and liver ; the 

 latter is even attached to this surface for a portion of its extent. 



On each side of the pillars, the circumference of the muscle forms an 

 arch which passes over the great and small psoas muscles. 



Action. The diaphragm, in contracting, tends to become an inclined 

 plane ; its central portion is carried backwards, and the antero-posterior 

 diameter of the chest is increased. It is, therefore, essentially an inspiratory 

 muscle. It may also raise the ribs by making the mass of abdominal viscera 

 its fixed point ; it then acts as a reflected muscle, to which these viscera serve 

 as a pulley. (The diaphragm also aids the other abdominal muscles in 

 expulsive efforts and, when affected with irregular spasmodic contractions, 

 produces the peculiar phenomenon in Man and some of the lower animals, 

 known as hiccough.) 



DIFFERENTIAL CHARACTERS OF THE DIAPHRAGM IN OTHFR THAN SOLIPED ANIMALS. 



In the Ox, the pillars of the diaphragm are very long and voluminous. " The 

 attachments of the muscular portion are much farther distant from the cartilaginous 

 circle than in the Horse, particularly at the' superior part ; this disposition explains the 

 innocuousness of puncture of the paunch in the middle of the last intercostal space; 

 for with the Horse, when the instrument is passed through this part, it penetrates the 

 thorax. Communicated to M. Lecoq by M. Tdbourin. 



In the Sheep we have not remarked that the costal attachments were more forward 

 than in the Horse. 



Rigot erroneously states that, in the Pig and Dog, the oesophagus passes between the 

 two pillars of the diaphragm ; on several occasions we have convinced ourselves that this 

 conduit traverses the right pillar, as in the other animals. 



COMPARISON OF THE DIAPHRAGM OF MAN WITH THAT OF ANIMALS. 



In the human diaphragm, the aponeurotic portion is divided into three leaflets, which 

 has caused it to be termed the aponeurotic trefoil. Between the middle and right 

 leaflet is the orifice through which the inferior vena cava passes. The openings for the 

 passage of the oesophagus and the aorta are situated between the two pillars. There are 

 frequently met with in Man one or two small accessory pillars, separated from the large 

 pillars by an aperture that affords a passage, on the right side, to the vena azygos and the 

 sympathetic nerve, and on the left side, to one of the lumbar veins and the other 

 sympathetic nerve. 



The peripheric muscular portion always joins, posteriorly, the central muscular portion. 



ARTICLE II. MUSCLES OF THE ANTERIOR LIMBS. 



These are divided into four principal groups : the muscles of the 

 shoulder, arm, fore-arm, and foot. 



