. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. the ventral half of the body, thus giving rise to the musculature of this region, while dorsally their extension is less marked (Fig. 11 3). In this process the myocommata also participate, so that the whole body is enveloped on either side by a series of muscle-plates, the fibres of which have a generally longitudinal direction, and are inter- rupted at regular intervals by the in- termuscular ligaments, the derivatives of the earlier myocommata. This primitive condition can readily be rec- ognized in the trunk region of a
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. the ventral half of the body, thus giving rise to the musculature of this region, while dorsally their extension is less marked (Fig. 11 3). In this process the myocommata also participate, so that the whole body is enveloped on either side by a series of muscle-plates, the fibres of which have a generally longitudinal direction, and are inter- rupted at regular intervals by the in- termuscular ligaments, the derivatives of the earlier myocommata. This primitive condition can readily be rec- ognized in the trunk region of a fish, but it becomes greatly modified in the Fig. 117. Illustrating the downward growth of the myotomes, e, epimere (myo- tome) ; m, mesomere. birds and mammals ; yet even here traces of the primi- tively segmented condition can be made out in the ventral abdominal region and in the intercostal muscles. In the fishes the result- ing muscles of the trunk and tail become subsequently di- vided into dorsal and ventral or epiaxial and hypaxial sys- tems, the line of division between the two following more or less closely the lat- eral line, and being marked by a partition of connective tissue. In the amphibia these epi- and hypaxial por- tions are clearly visible in the tail, but farther forward the hypaxial system is reduced. This reduction is carried to a greater extent in the aminotes, where almost the sole traces. Fig, 118. Transverse section through young Amblystoma, showing the final re- sult of the downward growth of the myo- tomes (deeply shaded) ; a, aorta ; c, car- dinal vein ; /, liver ; 0, oesophagus ; p, peritoneum; pg, pectoral girdle; r, rib ; J, subvertebral Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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