34 PROFESSOR STRUTHERS. 



Even when synovial surfaces occur in cetacean digits, the 

 motion can be only that of a little gliding on the nearly flat 

 surfaces. The cartilaginous nodes of the digits provide, by the 

 flexibility of the substance itself, for a certain amount of general 

 bending along the distal part of the paddle. 



The Terminal Cartilages of the Digits. The terminal carti- 

 lages of digits III. and Y. resemble each other in that there 

 is a cartilage attached to the distal bone, and a joint across 

 part of the cartilage. In digit III. the cartilage attached 

 to the distal end of the 8th bone is horse-foot shaped in out- 

 line, 2 inches across by If longitudinally (fig. 10). The joint 

 is situated J inch from the tip, is 1J to 1J inch in breadth, 

 reaching to J inch from the radial border and nearer to the 

 ulnar border, and goes through the whole thickness of the 

 cartilage. It is curved, the concavity towards the bone. The 

 joint is a soft part of the cartilage, and permits of motion. This 

 joint had the same position in both right and left digit III. 



In digit V. the cartilage, attached to the distal end of the 

 4th bone, is ovoid in outline, wanting the proximal fourth of the 

 ovoid where it is fitted on the phalanx ; is If inch across and 

 2| longitudinally. The joint is situated about f inch from 

 the junction with the phalanx, occupies the greater part of the 

 breadth, is sinuous but mostly with its concavity towards the 

 bone, and the cartilage bends at it readily. It was, however, 

 seen only on the flexor surface, and, on section, to go only a 

 third to half-way in from that surface. This was on the left 

 paddle ; in the right paddle no joint could be detected in the 

 distal cartilage of digit V 



In digit II. the cartilage, attached to the distal end of the 

 3rd bone, is very greatly expanded, is of broad horse-foot shape 

 in outline, 4J inches across, 3 inches longitudinally (fig. 11). 

 This cartilage forms most of the great hump on the radial 

 border of the paddle, is about midway between the radial 

 hump and the tip, and must give not only breadth but strength 

 and resistance to this part of the paddle. It presents two 

 joints, dividing it transversely and incompletely into three 

 nearly equal parts, the proximal of the two the most marked. 

 They are in part diarthrodial, in part formed by soft connective 

 tissue. Both have the concavity proximal, parallel to the end 



