40 THE POCKET ANATOMY 



side of tendinous expansion on dorsa of ist phalanges of 

 fingers(r) (2 outer median, 2 inner ulnar). [Flex metacarpo- 

 phalangeal and extend interphalangeal joints.] 



Interossei dorsales (4) : ist muscle (abductor indicts). Outer 

 head. From upper ^ of ulnar border of ist metacarpal(F). 

 Inner head. Radial border of 2nd metacarpal(F). The others 

 from posterior part of lateral surfaces of both metacarpals, 

 between which they lie ist and 2nd muscles to radial side of 

 ist phalanx of index and middle fingers respectively, 3rd and 

 4th in similar manner to ulnar side of middle and ring fingers 

 (T). Each is inserted partly into base of ist phalanx, and 

 partly into expansion of common extensor on ist phalanx(x) 

 (Ulnar). [Abduct fingers from middle line of hand i.e., 3rd 

 (middle) finger ; also same action as lumbricales.] 



Interossei palmares (3) : ist from ulnar side of 2nd meta- 

 carpal, 2nd and 3rd from radial sides of 4th and 5th meta- 

 carpals respectively (F) ist phalanx of finger from which they 

 arise and on the same side as the origin, and into extensor 

 tendon expansion(x) (Ulnar). [Adduct fingers towards middle 

 line, and same action as lumbricales.] 



MUSCLES AND FASCIA OF BODY. 



BACK, IST LAYER. 



Trapezius : spinous processes of all dorsal and 7th cervical 

 vertebrae, with supra-spinous ligaments, ligamentum nuchas, 

 inner Jrd of superior curved line of occiput(T) outer rd of 

 posterior border of clavicle, superior edge of acromion, superior 

 lip of posterior border of spine of scapula(F), and rough im- 

 pression on spine about i inch from root(T) (Spinal accessory, 

 3rd and 4th cervical by cervical plexus.) [A Upper fibres 

 draw scapula and clavicle upwards, lower fibres downwards, all 

 backwards ; B pulls head backwards, and also flexes to same 

 side.] Anterior margin forms posterior boundary of posterior 

 triangle of neck. 



Latissimus dorsi: spinous processes of lower 6 dorsal, 

 supra-spinous ligaments(A) ; from the posterior layer of the 

 lumbar aponeurosis, by which it is attached to all the lumbar 

 and sacral spines, and posterior of outer edge of iliac crest, 

 beyond this for i inch(p), lower 3 or 4 ribs(F), and occasionally 

 a slip from angle of scapula bottom of bicipital groove of 

 humerus(x) (Long subscapular). [Draws arm down and back- 

 wards, rotating inwards.] In the back the latissimus is posterior to 



