66 LANDMARKS MEDICAL AND SURGICAL. 



the tendon of the flexor carpi radialis. In feeling the pulse 

 it should be remembered that, in some cases, the superficialis 

 volae arises higher and is larger than usual. In such cases it 

 runs by the side of the radial artery, and gives additional 

 volume to the pulse. The old writers call it ' pulsus duplex.' 

 When in doubt, therefore, it is well to feel the pulse in each 

 wrist. 



143. Great carpal bursa. The great synovial sheath 

 under the annular ligament common to the flexor tendons 

 of the ringers and the long flexor of the thumb, extends, 

 upwards, about an inch and a half above the edge of the liga- 

 ment, and, downwards, as low as the middle of the palm. 

 This general synovial sheath communicates with the special 

 sheaths of the thumb and the little ringer ; not with that of 

 the index, middle, and ring ringers. . 



144. 'Tabatiere anatomique.' On the outer side of the 

 wrist we can distinctly see and feel, when in action, the three 

 extensor tendons of the thumb. Between the second and 

 third there is deep depression, at the root of the thumb, 

 which the French humorously call the ' tabatiere anatomique.' 

 In this depression we can make out I, the relief of the super- 

 ficial radial vein ; 2, the radial artery, in its passage to the 

 back of the hand ; 3, the upper end of the metacarpal bone 

 of the thumb. 



145. Tendons on back of wrist. The relative positions 

 of the several extensor tendons of the wrist and fingers, as 

 they play in their grooves over the back of the radius and ulna, 

 can all be distinctly traced when the several muscles are put 

 in action. The length of their synovial sheaths should be 

 remembered. They vary from one inch and a half to two 

 inches and a half. The longest of all are those of the extensors 

 of the thumb. When these sheaths are inflamed and swollen, 

 the motion of the tendons becomes painful and gives rise 

 to a feeling of crepitus, called ' tenalgia crepitans ' by some 

 writers. It is said to be met with sometimes in pianists. 



146. Lines of arteries. The course of the radial artery 

 corresponds with a line drawn from the outer border of the 

 tendon of the biceps at the bend of the elbow down the front 



