OCR Text |
Show 288 MESSRS. B. C. A. WINDLE AND F. G. PARSONS ON [Nov. 3, says that the costal origins do not interdigitate with the transversalis. Obliquus abdominis externus.-This muscle usually rises from a large number of ribs, as the following list shows :- Hippotamus (1) 4-15 Pig(H) 7-13 Chevrotain (20,22) 6-13 Sheep (43) 6-13 Harnessed Antelope (55) 5-12 Duiker-bok (54) 6-14 Tapir (62) 4-18 Horse (63) 4-18 Hyrax (75) 5-22 Elephant (81) 3-19 Elephant (72) 3-20 The insertion into the crest of the ilium is very slight, so that Poupart's ligament is not a well-defined structure as in Man. In the Horse the external abdominal ring is a large oval structure, but in the Ruminants it is a mere slit, the two pillars joining at the pubic attachment. The muscle is largely supported by the tunica elastica which lies superficial to it and is specially well-developed in the Solipeds, Ruminants, and Elephant. The SupracostaUs is the forward continuation of the external oblique; we have little doubt that it is always present in Ungulates, although it is so thin and transparent that it requires careful looking for, and many authors make no mention of it. It rises from the sternum opposite the second and third ribs and passes forward and outward, covering the anterior part of the rectus to be inserted into the first near the junction of the bone and cartilage. Obliquus abdominis internus.-This has a definite origin from the iliac crest and lumbar aponeurosis; it is much more fleshy in the hinder than in the fore part of the abdomen and is inserted into the cartilages of the hinder ribs. Myocommata are frequently found extending into it. Retractor ultimce costce.-Chauveau (II.) describes in the Horse a small oblique muscle lying dorsal to the quadratus lumborum, rising from the anterior lumbar costal processes and being inserted into the posterior border of the last rib ; he regards this as part of the internal oblique sheet, and we have little doubt that he is right since it is entirely in series with the internal intercostals. We have found the muscle in the Cervidae, Bovida?, and Tragulida?, and believe that it is present in all Ungulates (see text-fig 27, H p. 287). The Transversalis abdominis requires some little care to separate from the internal oblique, but, unlike that muscle, it is more fleshy in the anterior part of the abdomen, and is usually attached to the deep surfaces of about half the ribs-in the Chevrotain and Harnessed Antelope to the last six, in the Tapir and Horse to the last eleven. |