SOO TUE MUSCLES. 



1. Remove the skin from this region, and with it the panniculus carnosus, in order to study 

 the external surface of the abdominal tunic. 2. The dissection of the great oblique muscle is 

 accomplislied by removing the yellow fibrous envelope from the fleshy portion of the muscle, 

 together with the sterno-trocluneus. Tlie inguinal ring should be exposed by the ablation of 

 tije dartos muscle, the sheath and penis, or the mammae. 3. On the opposite side, the small 

 oblique is uncovered by excising tlie great oblique, leaving, however, that portion of the 

 aponeurosis which is mixed up with that of the first muscle. 4. The Litter havino' been 

 studied, dissect the great straight muscle of the abdomen on the same side, in separating from 

 the white line, by a longitudinal incision, the aponeurosis common to the two oblique muscles, 

 dividing this aponeurosis and the fleshy portion of the internal oblique by another incision 

 extending transversely from the umbilicus to the middle of the lumbar region, and laying back 

 one of the musculo-aponeurotic sections on the thigh, the other on the ribs. 5. The transverse 

 muscle is dissected on tlie same side as the external oblique has been. To expose it, nothing 

 more is necessary than to make two incisions simdar to the foregoing, but including the two 

 oblique and the straight muscle, throwing back tiie two portions as above. 6. Lastly, open 

 the entire abdominal cavity by cutting through the transverse muscle in the same way ; then 

 study the muscular digitations of that muscle, the internal orifice of the inguinal canal, and 

 the layer reflected from the aponeurosis of tue great oblique muscle. 



1. Abdominal Tunic (Tunica Abdominalis, Tunica Elastica). 



The vast expansion of yellow elastic fibrous tissue spread over the two 

 external oblique muscles of the abdomen is so named. 



^Verj thick towards the prepubic tendon of the abdominal muscles and in the 

 vicinity of the linea alba, this expansion gradually thins as it approaches the 

 sternum, and disappears near the abdominal insertion of the pectoralis magnus. 

 It also diminishes in thickness as it extends from the linea alba ; and when it 

 reaches the fleshy portion of the great oblique muscle it becomes reduced to an 

 extremely thin layer, the fasciculi of which separate more and more from one 

 another, until they completely disappear. Anteriorly, however, it is seen to be 

 prolonged on each side to the posterior digitations of the serratus magnus. 

 Posteriorly, it furnishes some bundles of fibres, which are detached from the 

 surface of the common tendon, and are carried between the thighs to be lost on 

 the internal crural muscles. 



The abdominal tunic is covered by the skin and panniculus carnosus, from 

 which it is separated by an abundance of connective tissue. In the male, its 

 external surface gives attachment to the suspensory ligaments of the prepuce, 

 and to the dartos ; and in the female, to the elastic capsule which envelops each 

 mammary gland. By its internal face, it closely adheres to the aponeurosis of 

 the great oblique muscle ; though it is easily separated from the fleshy portion. 

 It is traversed by several openings, which afford passage to the subcutaneous 

 vessels and nerves of the abdominal region. 



Use. — The abdominal tunic acts as an immense elastic girth or bandage, 

 which aids the muscles in sustaining the weight of the intestines. As the 

 digestive organs increase in volume, this tunic increases in thickness. 



In the Pig, Dog, and Cat, it is reduced to a simple cellulo-aponeurotic layer, owing to 

 the stoinaoh and intestines in tiiese animals exercising but a small amount of pressure on the 

 abdominal parietes. 



2. White Line (Linea Alba). 



The white line {Unm alha) is a fibrous cord comprised between the internal 

 border of the two great straight muscles, and is considered as being fonned by 

 the intercrossing, on the median line, of the aponeuroses belonging to the oblique 

 and transverse muscles. Attached, in front, to the inferior surface of the xiphoid 



