■246 TBE MUSCLES. 



separates the skin from the aponeurosis of the great oblique. The muscular portion of 

 this muscle has no attachment to the aponeurosis of the great dorsal. 



The aponeurosis of the small oblique is divided into two lamellaj at the external 

 border of the great straight muscle ; the anterior is consolidated with the great oblique, 

 and passes in front of the great straight ; the posterior is united to the transverse, and 

 passes behind that muscle. 



The aponeurosis of the transverse is divided into two leaves, only one of which remains 

 behind the great straight muscle ; this is named the semilunar fold of Douglas. 



The great rectus muscle of the abdomen offers three transverse fibrous intersections in 

 its length (Unex transversx). At its upper extremity, it divides into three branches ; 

 the internal is attached to the xiphoid appenda<;e and the cartilage of the seventh rib ; 

 the middle, to that of the sixth rib ; the external, to the cartilage of the fifth rib. 



" To the great rectus is annexed a small triangular muscle, the pyramidal, which is 

 not found in animals. This muscle is about 2J inches long ; is sometimes absent ; most 

 developed in children ; is attached by its base to the pubis, between the spine and the 

 symphysis ; and by its stmimit is continuous with a tendon which is lost in the white 

 line, and constitutes, with that of the opposite side, a fibrous cord which may be followed 

 to the umbilicus." — Beaunis and Bouchard. 



Lastly, at the inner aspect of all the abdominal muscles, beneath the peritoneum, is 

 a fibrous lamella — the/os«'a transversalls. This fascia is not distinctly limited upwards 

 or outwards ; below, it is fixed to the craral arch, in the vicinity of the inguinal canal, 

 and sends a layer to the surface of the cord spermatic. 



DIAPHRAGMATIC REGION. 



This is composed of a single muscle, the diaphragm. 



Diaphragm. 



Preparation. — Place the subject in the first position ; open the abdomen and remove 

 the viscera it contains, as well as the large vascular trunks lying upon the sablumbar 

 region ; detach the peritoneum from the fieshy portion of the muscle, in order to show 

 the digitations of the latter more distinctly, taking care not to allow the air to enter the 

 thoracic cavity, as it would destroy the tense and concave form of the diaphragm. 



Situation — Direction. — The diaphragm is a vast musculo-aponeurotio 

 partition separating the thoracic from the abdominal cavity, between which 

 it is placed in an oblique direction downwards and forwards. 



Form. — It is flattened before and behind, elliptical, wider above than 

 below, concave posteriorly, and convex anteriorly. 



Structure. — This muscle comprises: 1, A central aponeurotic portion 

 designated the phrenic centre, which is incompletely divided into two folioles 

 (leaflets) by the pillars— Qeshy columns which descend from the sublumbar 

 region; 2, A peripheral (or circumferential) portion forming a wide 

 muscular band around the phrenic centre. 



The phrenic centre (also named the speculum Helmontii or mirroiT of 

 Helmont) is composed of white, glistening, radiating fibres which, originating 

 from the pillars, extend in every direction to join the muscular fibres of the 

 peripheral portion. It is pierced, in its right leaflet, by a large opening for 

 the posterior vena cava. 



The pillars are two in number, a right and left. The right pillar, the 

 most considerable, is a very thick, fleshy fasciculus which commences under 

 the loins by a strong tendon, united to the inferior common vertebral liga- 

 ment. It descends to the phrenic centre, to which it gives a heart-shaped 

 appearance. Near its inferior extremity, it presents an opening for the pas- 

 sage of the oesophagus into the abdominal cavity. — The left pillar is a small 

 triangular fasciculus, partly separated from the preceding by an orifice for 

 the transmission of the posterior aorta and the thoracic duct. It also arises 



