280 ANATOMY IX A NUTSHELL. 



Obliquus capitis inferior. — Description. — This muscle is larger than the 

 superior one. 



Origin.— Apex of axis. 



Insertion. - Lower and back part of transverse process of atlas. 



A.< riON. — To rotate the arias with cranium. 



The -kin of the back is supplied by posterior divisions of spinal nerves. 

 The internal branch of the posterior divisions of the upper six dorsal uerves are 

 cutaneous, while the external branches of the posterior divisions of the lower 

 six dorsal nerves are cutaneous. The external divisions of the upper and 

 the internal divisions of the lower six have no cutaneous distribution. 



The sacro-vertebral articulation is supplied by the fourth and fifth lumbar and 

 sympathetic nerves. The costo-central articulations are supplied by the an- 

 terior divisions of the spinal nerves. The costotransverse articulations are sup- 

 plied by the posterior division- of the spinal nerves. The sacro-iliac articu- 

 lations are supplied by the posterior divisions of the first and second sacral 

 nerves, the superior gluteal nerve, and sacral plexus. The saero-eoccygeal 

 articulation is supplied by the fourth and fifth sacral and coccygeal nerves. 

 The ribs and vertebra' an- supplied by the gray rami communicantes. 



LESSON LXXVIII. 

 Triaxoles of the Neck. (Plate XIV.) 



The side of the neck is in the form of a rectangle, bounded, above by the 

 lower margin of the jaw-bone and a line continued from the angle of the jaw to 

 the mastoid process; below, by the clavicle; posteriorly, by the Trapezius; and 

 anteriorly by the median line of the neck. This rectangle is divided into two 

 triangles by the Sterno-cleido-mastoid. The anterior one is bounded in front 

 by an imaginary line behind by the Sterno-cleido-mastoid. and above by the 

 lower jaw-bone. The posterior one i- bounded in front by the Sterno-cleido- 

 mastoid, behind by the Trapezius, and below by the clavicle. The Omo-hyoid 

 divide- these triangles into two others and the Digastric divides the upper one 

 of the anterior triangles into two other triangles. The Digastric pierces the 

 Stylo-hyoid which help- to make the boundary line of the sub-maxillary tri- 

 angle. Then these muscles divide the rectangle on the side of the neck into five 

 triangles, (li Tin. [nferiok carotid triangle, or triangle of necessity, 



of Ml -( ! I.\i; TRIANGLE. (2) TtlE SUPERIOR CAROTID TRIANGLE, or TRIANGLE 

 01 ELECTION. (3) Till. SUBMAXILLARY, Or DIGASTRIC TRIANGLE. (4) THE 

 OCCIPITAL TRIANGLE. (5) Till. SUBCLAVIAN, Or SUPRACLAVICULAR TRIANGLE. 



All these five triangles have a roof, boundary lines, and contents. The roof of 

 them b made by skin, superficial fascia. Platysma myoides, and deep fascia. 

 The Inferior carotid triangle in addition to this has the superficial cervical nerve 

 ramifying in it- roof. Righl beneath this roof are the Sterno-hyoid and Sterno- 

 thyroid. By -one these two muscles are called the floor, hut the Longus colli 

 and Scalenus amicus and pari of the Rectus capitis anticus major form the floor. 

 This triangle is bounded in fhont by the median line. above by the anterior 



