206 THE MUSCLES. 



vertebra after the tenth, and to some lumbar vertebrae. Its digitations 

 are fixed to the posterior border and external face of the nine last ribs. 



3. Relations. Outwards, with the great dorsal; inwards, with the 

 small anterior serratus, the ilio-spinalis, common intercostal, and the 

 external intercostals. Some of its posterior digitations are partly con- 

 cealed by those of the great oblique muscle of the abdomen; the last, 

 indeed, is entirely covered by that muscle. 



4. Action. This is an expiratory muscle, in consequence of its drawing 

 the ribs backwards and upwards. 



5. The Ilio-spinalis Muscle. (Fig. 106.) 



Synonyms. It represents the long dorsal, short transversal, and long spinous of 

 Bourgelat. Cuvier and others have described it as consisting generally, in mammalia, 

 of five particular muscles, designated as longissimus dorsi, transversalis cervicis, semi- 

 spinalis dorsi, and semispinalis colli. It corresponds to the longissimus dorsi, and trans- 

 versalis cervicis of Man. 



(Percivall designates this important muscle the longissimus-dorsi the name given to 

 its analogue in Man. By Girard, Leyh, and Chauveau, it is styled the ilio-spinalis.) 



Extent Situation. This, the most powerful and complex of all the 

 muscles in the body, extends along the dorso-lumbar spine, above the 

 costal arches, from the anterior border of the ilium to the middle of the 

 cervical stalk. 



Form. It is elongated from before to behind, and flattened above 

 and below in its posterior half, which represents the common mass in Man ; 

 this mass is prismatic in form, thick inwards, and thin outwards. Anteriorly, 

 it is flat on both sides, and bifurcates into two voluminous branches, a 

 superior and inferior, between which pass the insertions of the complexus 

 to be fixed into the transverse processes of the first dorsal vertebras. 



Attachments. 1, Upon the lumbar border, the external angle and 

 internal surface of the ilium, the sacro-iliac ligament, and the sacrum ; 

 'J, To the spinous processes of all , the lumbar and dorsal, and last four 

 cervical vertebrae ; 3, To the articular tubercles of the lumbar vertebra and 

 the transverse processes of all the dorsal, and the last four cervical vertebras ; 

 4, To the costiform processes of the lumbar vertebrae, and the external 

 surface of the fifteen or sixteen last ribs. 



Structure. If this muscle is examined posteriorly, in the part which 

 forms the common mass, it will be found to be composed of very compact 

 fleshy fibres, covered in common by a thick aponeurosis. These fibres 

 commence at the posterior extremity of the muscle, and all proceed forward, 

 stopping to take successive insertions on the various bony eminences 

 in its track, and forming three different orders of fasciculi, which are 

 more or less tendinous at their anterior or terminal extremity. These 

 fasciculi are internal and superficial, internal and deep, and external. 



The internal and superficial, or spinal fasciculi, pass to the summits of 

 the spinous processes already noticed when speaking of the attachments. 

 These fasciculi are little, if at all distinct posteriorly ; but they become 

 more so anteriorly. About the sixth dorsal vertebra, they separate from 

 the other fasciculi to form the superior branch of the muscle (Fig. 106, 3). 



The internal and profound, or transverse fasciculi, are those which attach 

 the muscle to the articular tubercles of the lumbar vertebrae and transverse 

 processes of the back and neck. They are well detached from each 

 other, even posteriorly, and are very tendinous. Anteriorly, they pass 

 into the inferior branch of the ilio-gpinalis, which they, in common with 



