no THE UPPER EXTREMITY 



quadratus it pierces the interosseous membrane, and gains 

 the dorsal aspect of the limb. 



It supplies rami musculares to the three deep muscles with 

 which it is in contact. In addition to these it gives off the 

 following branches : 



1. Median. 



2. Medullary. 



3. Anterior communicating. 



The a. mediana is a long delicate vessel which accom- 

 panies the median nerve. The medullary arteries are two in 

 number one for the radius, the other for the ulna. They 

 enter the ' nutrient foramina of these bones. The anterior 

 communicating is a slender artery, which runs distally, behind 

 the pronator quadratus, to join the volar carpal arch. 



Nervus Interosseus Volaris (O.T. Anterior Interosseous 

 Nerve). This is a branch of the median, and accompanies 

 the artery of the same name. It does not follow it, however, 

 through the interosseous membrane, but is distributed entirely 

 upon the volar aspect of the limb. It is the nerve of supply 

 for the flexor pollicis longus, the lateral part of the flexor 

 digitorum profundus, and the pronator quadratus, whilst its 

 terminal filament proceeds distally, behind the last-named 

 muscle, to help in the supply of the carpal joints. 



The flexor digitorum profundus is therefore supplied by 

 two nerves, viz. the ulnar and the median. The precise 

 range of supply by each of these nerves is somewhat variable. 

 As a general rule the division of the muscle which belongs to 

 the index finger is supplied by the median and the part 

 belonging to the little finger by the ulnar ; whilst the portions 

 belonging to the middle and ring digits receive filaments from 

 both nerves. 



WRIST AND PALM. 

 In this dissection we meet with the following structures : 



1. M. palmaris brevis and the volar cutaneous nerves. 



2. Aponeurosis palmaris. 



3. Arcus volaris superficialis and its branches. 



4. Median and ulnar nerves and their branches. 



5. Lig. carpi volare, lig. carpi transversum, the flexor tendons, and their 



vaginae mucosae. 



6. Mm. lumbricales. 



7. Short muscles of the thumb and little finger. 



8. Arcus volaris profundus and its branches. 



9. Arteria princeps pollicis and art. volaris indicis radialis. 



