GENERAL MORPHOLOGY OF THE MUSCLES. 185 



for a man of 150 lbs. weight : skeleton, 27 lbs. ; muscles, 63 lbs. ; 

 viscera (with skin, fat, blood, &c.), 60 lbs. 



General Morpholog-y. — It cannot be doubted that the disposition of the 

 muscles, as a whole and in groups, originally bears a close relation to the plan 

 of vertebrate organization in the skeleton. This is very perceptible in the earlier 

 stages of foetal development and in the lowest vertebrate animals. In fishes 

 especially, and partly in amphibia, the muscles present a remarkable degree of 

 vertebrate segTuentation, the greater pai-t of the muscles of the trank being 

 subdivided into zones, or myotomes, by partitions or sclovtomes, partly bony 

 and partly cartilaginous or membranous, which extend transversely through the 

 walls of the trunk, and which correspond in number and position with the 

 veiiiebral and costal segments. In the higher animals and in man, together 

 with the greater specialization of muscles in connection with the development 

 of limbs, great deviations from the primitive muscular type in the trunk have 

 occurred^ and it becomes extremely difficult to trace the morphological relations 

 of the rest of the muscles in the axial part of the body. It is indeed only in 

 the deeper muscles of the vertebral column and of the ribs that the vertebrate 

 subdivision and relation remain in any degree apparent. In the more super- 

 iiciai muscles, and more especially ia the muscles of the limbs, where the direc- 

 tion of the fibres is generally outwards from the tiimk, i^ortionsof the myotomes 

 iiin together so as to form muscles of greater or less length, and ui which all 

 appearance of vertebrate division is effaced. In their more general relations 

 also to the trunk of the body two sets of the muscles may be distinguished 

 as cpaxial and Injpaxlal (episkeletal and hyijoskeletal of Huxley), according as 

 they lie above or below the embryonic vertebral axis and the jjlane of its lateral 

 extension. The lujpax'tal muscles, comparatively little developed in man, com- 

 prise chiefly the prevertebral muscles of the neck with the psoas and pyrifonnis. 

 Of the cpaxlal muscles a dorui-Jatcrnl division consists mainly of the long and 

 short erector muscles of the spine and head ; while a rentro-latcrnl division con- 

 sists both of such ventral longitudinal muscles as genio-hyoid, stenio-hyoid, and 

 recti abdominis, and of the lateral, obliquely directed, sterno-mastoid, scalene, 

 intercostal, and abdominal muscles. The muscles of the limbs are also primarily 

 derived from this great ventro-lateral muscle. Thej- may be distinguished as 

 extrinsic when attached partly to the limbs and partly to the tiimk, and as 

 ■intvinsic when wholly attached to the bones of the limbs and then- arches. 



To these morphological relations further reference vdW hereafter be made 

 under the several large divisions of the muscles. (See Hmnphry, " Obsei*vations 

 in Myology," &c., 1872, and in various papers in the Joiu-n. of Anat. ; Huxley, 

 " Anat. of Verteb. Animals," and Mivart. " Lessons ia Elementary Anatomy." 



Varieties. — It foUows from what has been stated above, that homologous 

 correspondence can be traced between the individual muscles and groups of 

 muscles of man and those of animals. But as the form and attachments 

 of the muscles are subject to very great variations in different animals, as well as 

 to occasional varieties in the same species, the detei-mination of the special homo- 

 logies is attended in many cases Avith gi-eat difficrdty, and is still very imperfect. 

 Many varieties have also been observed in the hmnan body, and it is interesttag 

 to notice that these varieties are found to reappear generally in the same fonn, 

 or ill modifications of it which indicate relations to a tj-jiical or fundamental 

 structure ; and that many of them are *hus more or less repetitions of forms 

 known to exist ia dift'erent species of the lower animals. (Consult John Wood 

 in Proceedings of Ptoy. Soc. 18G4-7, and Turner and others in Journ. of Anat. & 

 Physiol. : Macalister's Instructive Catalogue of Muscular Anomalies, in Trans. 

 Roy. Irish Acad., 1872, and other papers ; Hallet, in Edta, Med. Joirni., ISio ; 

 Wenzcl Gruber, in Mem. of the Petersburg Acad.) 



FASCIiE. 



The terra Fascia is applied to parts presentin.ii a membranous dispo- 

 sition of reticulated or felted fibrous tissue. These structures have 

 usually been distinguished as the superficial and the deep; the former 

 oousistinf^ of looser and finer material, and passing by their slenderer 



