MUSCLES OF THE TRUNK 215 



fixed into the transverse processes of the majority of the lumbar vertebras, 

 and the inner face of the two or three last ribs. 



Relations. By its upper face, with the intertransversales, the small 

 retractor of the last rib, and the fibrous fascia which unites that muscle to 

 the small oblique of the abdomen. By its inferior face, to the great psoas. 



Actions. It draws the last ribs backwards, and inclines the lumbar spine 

 to one side. 



6. Intertransverse Muscles of the Loins. (Fig. 109, 2, 2.) 

 (Synonym Intertransversales luniborum Percivall.) 



These are very small flat muscles which fill the intervals between the 

 transverse processes of the lumbar vertebras. The muscular fibres entering 

 into their composition are mixed with tendinous fibres, and are carried from 

 the anterior border of one transverse process to the posterior border of the 

 other. 



They respond, by their superior face, to the ilio-spinalis (longissimus 

 dorsi), and by their inferior face to the quadratus, as well as the psoas 

 magnus. They act by inclining the lumbar region to one side. 



DIFFERENTIAL CHARACTERS OF THE MUSCLES OF THE SUBLUMBAR REGION IN OTHER 

 THAN SOLIPED ANIMALS. 



In Ruminants and the Pig, the muscles of this region so closely resemble those of 

 Solipeds, that a special description is unnecessary. 



In the Dog, the great psoas is little developed, and only commences at the third, or 

 even the fourth lumbar vertebra; the iliac psoas is very slender, particularly in its 

 external portion ; otherwise it is scarcely distinct from the great psoas, with which it may 

 be said to form one muscle ; the small psoas is relatively larger than the great ; it is not 

 prolonged into the pectoral cavity, and its anterior extremity is confounded with the 

 quadratus lumborum, which is longer and stronger than in all the other animals. 



COMPARISON OF THE SUBLUMBAR MUSCLES OF MAN WITH THOSE OF ANIMALS. 



In human anatomy, by the names of psoas and iliacus are described the great psoas 

 and iliac psoas of anunals. The psoas magnus of MAN is distinguished from that of 

 Solipeds by its superior insertions, which do not go beyond the last dorsal vertebrae. 



The small psoas is often absent ; when present, it is attached, above, to the bodies of 

 the twelve dorsal vertebrae, below, to the ilio-pectineal crest. 



The intertransversales have been studied with the muscles of the back. The 

 quadratus of the loins, classed by anthropotomists with the abdominal muscles, is 

 distinctly divided into three series of fasciculi : ilio-costal fasciculi, which pass from the 

 upper border of the ilium to the twelfth rib ; lumlo-costal fasiculi, passing from the 

 transverse processes of the three or four last lumbar vertebrae to the twelfth rib, and ilio- 

 lumbar fasciculi, going from the iliac crest to the posterior face of the transverse processes 

 of all the lumbar vertebrae 



COCCYGEAL REGION. 



This region is composed of four pairs of muscles destined for the 

 movements of the tail : three, named the sacro-coccygeal, are disposed 

 longitudinally around the coccygeal vertebrae, which they completely 

 envelop ; the fourth is designated the ischio-coccygeus. 



1. Sacro-coccijgeal Muscles. (Fig. 131, 1, 2, 3.) 



These three muscles are inclosed, with those of the opposite side, in a 

 common aponeurotic sheath which is continuous with the inferior ilio-sacral 

 and sacro-ischiatic ligaments. They commence on the sacrum, are directed 

 backwards and parallel with the coccyx, gradually diminishing in thickness, 

 and are decomposed into several successive fasciculi terminated by small 



