ANATOMY OF MEGAPTERA LONGIMANA. 43 



13. PROPORTION OF CARTILAGE TO BONE IN THE FINGERS. 

 The extent to which each finger is formed of bone and of cartilage 

 in these two whales is seen in Table IV. In the B. musculus 

 (50-feet-long) the proportions are to be taken as approximative 

 only, as in a more mature state the distal cartilages would be 

 in part ossified. But the proportions in my 64-feet-long B. 

 musculus correspond pretty well, being, of bone and cartilage, 

 respectively, in digit II, 18| and 6J inches ; digit III., 25 and 

 8J ; digit IV., 22J and 8 J ; and in digit V., 14 and 5. The 

 comparison is most reliable on the two long digits. In the 

 Megaptera, the great terminal cartilage gives digit II. a large 

 percentage of cartilage, but in all its digits the percentage of 

 cartilage is greater than in B. musculus. The high percentage 

 of cartilage in digit IV. of Megaptera is to some extent gained 

 by the 8th element not being ossified, but is mainly owing to 

 the relative shortness of the more distal bones of the digit. 

 It would appear, therefore, that the great length of the fingers 

 in Megaptera, compared with those of B. musculus, while 

 mainly obtained by bone, is in still larger proportion gained by 

 cartilage. This should allow of greater flexibility, but may be 

 regarded rather as related to the greater robustness of the bones 

 in Megaptera. The large amount of cartilage in the fingers 

 of the cetacea, reaching in these two whales to about from ^ 

 to j^j of the whole length of the digit, may be regarded as an 

 adaptation to general flexibility in digits so ensheathed that 

 their constituent bones cannot be moved separately. 



14. ADAPTATIONS OF THE NODES AND PHALANGES TO EACH 

 OTHER IN NEIGHBOURING FINGERS. The alternating nodes and 

 hollows fit into each other more closely than would appear 

 from the skeleton. The nodes are very large, most prominent 

 at the middle where they project J to f inch on each side 

 beyond the level of the expanded ends of the bones. On the 

 surfaces, flexor and extensor, the nodes do not rise above the 

 level of the enlarged ends of the bones, except to form a gentle 

 convexity. The great enlargement is in the breadth. Stated 

 generally, the nodes are about three times as broad as the narrow 

 part of the phalanges at the middle of the shaft. The bones 

 and the nodes, both invested in their thick fibrous covering, form 



