MUSCLES OF THE HAND. 



the middle of the back part of the ulna. It is a small 

 muscle, concealed by the extensor ulnaris and communis. 

 It ends in a tendon which passes along the same groove 

 with the extensor communis, beneath the annular ligament, 

 and is inserted with the tendon of that muscle into the 

 back part of the second and third phalanges of the fore 

 finger. Function. To extend the fore finger.* 



MUSCLES OF THE HAND. 



Dissection. Make an incision from the wrist along the 

 middle of the palm to the base of the fingers ; make a second 

 incision crossing the first transversely about its centre, now 

 reflect the integuments to either side, which will lead to the 



* During the dissections in the winter of 1849-50, in the Baltimore Col- 

 lege of Dental Surgery, a muscle was seen in connection with the indicator 

 which seems to be entirely new, or at least not present in the dissections of 

 anatomical writers, as we cannot find that they make any mention of it. We 

 have thought the name of Extensor Jlccessorius Jndicis not inappropriate. We 

 will quote the explanation given of this muscle, from the April number, 1850, 

 of the Medical Examiner. " It had its origin on the right hand by a delicate 

 tendinous membrane, from the radio-carpal articulation, behind the posterior 

 annular ligament, and in the same groove with, and posterior to the tendons of 

 the extensor communis and indicator, forming 

 a fleshy bulb nearly the size of the plantaris 

 of the leg. It soon, however, divided into two 

 bellies the one short and attached or inserted 

 by a delicate tendon, into the tendon of the in- 

 dicator, near the base of the metacarpal bone 

 of the fore finger the other larger, and con- 

 nected also to the indicator, but near the 

 articulation of the metacarpal bone with the 

 first phalanx of the fore finger, and also by a 

 narrow tendon, as seen in the drawing. On 

 the left hand the muscle had but one belly, 

 which ended in a tendon having a similar at- 

 tachment and resemblance to the larger belly 

 upon the right. Its function seems evidently 

 to assist the indicator in the extension of the 

 fore finger. Fig. 231 exhibits the muscle as 

 seen from the dissection. 



" a a Posterior annular ligament laid open. 6 Origin of the new muscle . c Its 

 smaller belly. <Hts greater belly, h Tendinous insertion of smaller belly. 

 g Tendinous insertion of larger belly, e Indicator. /Extensor communis 

 turned to one side to expose the origin of the new muscle, i Extensor longus 

 pollicis." 



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