ON THE MOVEMENT OF THE LOWER END OF THE 

 EADIUS IN PRONATION AND SUPINATION, AND 

 ON THE INTEROSSEOUS MEMBRANE. By James 

 F. Gemmill, M.A., M.D. 



This paper naturally divides itself into two parts, the first 

 dealing with the movement of the lower end of the radius, and 

 the second with the action of the main sheet of the interosseous 

 membrane during pronation and supination. 



I. 



There is a curious discrepancy in the teaching of anatomists 

 as to where the axis of the circumduction curve described by 

 the lower end of the radius lies in relation to the head of the 

 ulna. By Ellis ^ the axis of this curve is said to pass through 

 the styloid process of the ulna. Quain's text-book- contains 

 the same statement, but indicates that the insertion of the apex 

 of the triangular ligament is meant. In the greater number of 

 text-books the place of insertion of the triangular ligament at 

 the root of the styloid process is definitely stated to be the 

 centre of the circumduction curve, this ligament being supposed 

 to act as a fiexible or movable spoke to hold the radius against 

 the ulna as it rotates in the arc of a circle (Morris).^ 



The following authors give this view : — Morris, loc. cit. ; 

 Cleland and Mackay, Human Anatomy, p. 157; Cruveilhier, 

 Traite d' Anatomic Descriptive, 1871, vol. i. p. 366; Debierre, 

 Anatomic de VHomme, p. 231 ; Gegenbaur (French translation), 

 Trait6 d' Anatomic, 1889, p. 292; G. M. Humphry, Treatise on 

 the Human Skeleton, 1858, p. 425 ; Todd's Cyclopedia of Anatomy 

 and Physiology, vol. iv. p. 230 ; etc. 



F. 0. Ward,^ on the other hand, states that the centre of 

 curvature of the lesser sigmoid cavity of the radius is also the 



^ DemoTistratmis of Anatomy, 1890, p. 326. 



- Tenth edition, vol. ii. pt. ii. p. 170. 



^ Aiuttohvj of the Joints of Man, 1879, p. 261. 



■* F. 0. Ward, Outlines of Human Osteology, p. 222. 



