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ANATOMY OF VERTEBRATES. 



or lower half of the myocommas in the 

 trunk, fig. 140, 6, has been held to represent 

 the obliquus externus abdominis ; but, as it 

 is segmented by aponeurotic prolongations of 

 the short pleurapophyses, both in the abdo- 

 s minal and caudal regions, it is more like a 

 series of intercostals. The broad, thin, car- 

 neotendinous sheets, called ' external ' and 

 ' internal oblique ' muscles in Mammals, hav- 

 ing their fibres running in opposite directions, 

 may, indeed, be referred to the same system 

 of segmental trunk-muscles ; but this grade 

 of differentiation is not reached in Fishes 

 and fish-like Batrachians. The medial parts 

 of the haemal myocommas are more distinct, 

 and show more of the character of a longi- 

 tudinal muscle with tendinous intersections, 

 like the ' linea? transversa? ' of the human 

 ' rectus abdominis ;' and this muscle is one 

 of the determinable homologues of a recog- 

 nisable tract of the myocommas of the fish 

 and newt. In the Salamander, however, 

 the tract, fig. 141, s, is as superficial as that 

 part of the sheath of the ' rectus abdominis ' 

 in Mammals ; and it forms a corresponding 

 part of the sheath of a deeper-seated longi- 

 tudinal muscle, fig. 141, 7. Both 7 and 8 

 are specialisations of the lowest haemal por- 

 tions of the myocommas : they are anteriorly 

 resolved, or continued, as in Fishes, into 

 muscles acting upon the scapular, hyoidean, 

 and mandibular arches. The jnibohyoideus, 



7, arises from the pubis and outer part of 

 the gristly hamiapophysis, or Y-shaped 

 cartilage, fig. 113, d; it runs forward 

 in a sheath, analogous to that formed 

 by the aponeurosis of the external and in- 

 ternal oblique muscles of Mammals, and is 

 inserted into the ceratohyal. The muscle, 



8, called rectus abdominis, by Funk, 1 has its 

 attachment to the pubis through the medium 

 of the Y-shaped cartilage, which represents 

 the marsupial bones and tendinous ' pillars 

 of the abdominal ring ' in Mammals : it is 



Muscles of Salamandraterrestris. 



CLXXXVJ i. 



CI.XXXVII. 



