ANATOMY IN A NUTSHELL. 87 



Each tendon opposite the metacarpophalangeal articulation becomes nar- 

 row and thickened and gives off a thin fasciculus upon each side of the 

 joint, which blends with the lateral ligament and serves as a posterior lig- 

 ament; after having passed the joint it spreads out into a broad aponeurosis 

 which covers the whole of the dorsal surface of the first phalanx, being rein- 

 forced in this situation by the tendons of the Interossei and Lnmbricales. 

 Opposite the first phalangeal joint this aponeurosis divides into three slips, a 

 middle and two lateral. 



Origin. — (1) External condyle of humerus by common tendon; (2) deep 

 fascia; (3) intermuscular septum. (Plate XXIII.) 



Insertion. — Into the second and third phalanges of the fingers in the fol- 

 lowing manner; the outermost tendon accompanied by the Extensor indicis, 

 goes to the index finger; the second tendon is sometimes attached to the first by a 

 thin transverse band and receives a slip from the third tendon ; it goes to 

 the middle finger; the third tendon gives off a slip to the second and receives 

 a very considerable part of the fourth tendon ; the fourth or innermost 

 tendon, after dividing, sends one slip to join the third tendon; the other, rein- 

 forced by the Extensor minimi digiti, goes to the little finger. After the di- 

 vision of the aponeurosis opposite the phalangeal joint, the middle slip is in- 

 serted into the base of the second phalanx, while the two lateral are continued 

 onward along the sides of the second phalanx and are inserted into the dorsal 

 surface of the last phalanx. (Plate XXVI.) 



Action. — To extend the fingers. 



Nerve Suplpy. — Seventh cervical through the posterior interosseous. 



Blood Supply. — Posterior interosseous. 



Extensor minimi digiti. — Description. — (Plate XXXII.) — This is a 

 slender muscle placed on the inner side of the Extensor communis digitorum 

 with which it is generally connected. Its tendon runs through a separate 

 compartment in the annular ligament behind the inferior radio-ulnar joint, 

 then divides into two as it crosses the hand, the outermost division being joined 

 by the slip from the innermost tendon of the common extensor. The two slips 

 thus formed spread into a broad aponeurosis and receive a slip from the Ab- 

 ductor minimi digiti. 



Origin. — Common tendon by a thin tendinous slip and intermuscular 

 septa. (Plate XXIII.) 



Insertion. — Second ami third phalanges of the little finger. ( Plate XXVI.) 



Action. — Extends the little finger. 



Nerve Supply. — Seventh cervical through the posterior interosseous. 



Blood Supply. — Posterior interosseous and radial. 



Anconeus. — Description. — This is a small triangular muscle placed be- 

 hind and below the elbow-joint, and appears to be a continuation of the external 

 portion of the Triceps. Its filters diverge from their origin, the upper ones 

 being directed transversely, the lower obliquely inward. (Plate XXXII.) 



Origin. — External condyle of humerus posteriorly. (Plate XXII.) 



Insertion. —Side of olecranon process and upper fourth of posterior sur- 

 face of shaft of ulna. (Plate XXIV.) 



