78 PHYSIOLOGICAL SERIES. 



"WRIST. 



B. 146. Right wrist-joint of a Duck-billed Platypus (Ornitho- 

 rhynchus anatinus). The scaphoid and lunar are fused to 

 form a single bone articulating \vith the radius and to a 

 slight extent with the ulna. Two large lateral prominences 

 on its proximal surface engage with corresponding 

 depressions upon the radius and ulna, while the groove 

 between them is occupied by a process of the radius. This 

 interlocking between the proximal row of carpals and the 

 bones of the fore-arm restricts the movements of the wrist 

 to simple flexion and extension. 



B. 147. Left wrist-joint of a Spider Monkey (Atelesmelanocktr). 

 An interarticular fibro-cartilage (triangular cartilage) is 

 inserted between radius and ulna in the distal radio-ulnar 

 joint. The articulation between the ulna and the cuneiform 

 bone is separated by an antero-posterior septum from that 

 between the radius and the scaphoid and semilunar. 



B. 148. Left wrist-joint of Papio \_Cynoceplialus] sphinx. The 

 posterior radio-carpal ligament consists of two fasciculi, 

 that converge from their separate origin on the radius to 

 a common insertion on the cuneiform. The styloid process 

 of the ulna is prominent and articulates with the cuneiform 

 and pisiform bones. There is a partial septum between the 

 two halves of the joint. Presented l>y Prof. F. G. Parsons. 



B. 149. A dissection showing the fibro-cartilage at the radio- 

 ulnar articulation of the left side of a Man. 0. C. 268 A. 

 Corner, Jour. Anat. & Physiol., vol. xxxii. 1898, p. 272. 



DIGITS. 



B. 150. A vertical section of the fore-foot of a Horse (Eyuus 

 caballus) . 



In this are illustrated all the contrivances for augmenting 

 the moving powers, and diffusing the concentrated forces 

 of pressure and percussion. 



The interphalangeal joints are imperfect hinges, that 

 allow of slight lateral movements in addition to those of 



