32 PROFESSOR STRUTHERS. 



In both the 50-feet-long B. musculus and the B. borealis, 

 the carpal bones are well ossified, especially those of the first 

 row, except the pisiform which remains entirely cartilaginous in 

 all of them. This contrasts with the little progress ossification 

 has made in the carpus of this 40-feet-long Megaptera. 1 



9. THE CARTILAGES AND JOINTS OF THE DIGITS. The carti- 

 laginous enlargements between the digital bones are greatly 

 developed in Megaptera. Each of these nodes is composed of 

 the two epiphysial cartilages, separated by a more or less 

 developed synovial cavity. 2 



Mode of Articulation. The perichondrium enveloping the 

 node is, like the periosteum, about f inch thick, and, without 

 removing this membrane, a transverse depression is seen indi- 

 cating the presence of a joint. In the earlier nodes the position 



1 Vascular Canals of the Cartilages in Cetacea. It may be noted here that these 

 and all masses of cartilage in cetacea are pervaded by channels for red blood- 

 vessels, resembling the system of Haversian canals in bone. On separating the 

 epiphysial cartilages of the digits from their phalanx, the contained blood-vessels 

 are seen like a sj'stem of cordage passing from the bone into the cartilage, stretch- 

 ing for about an inch before they give way. In vertical transverse sections they 

 are seen as rounded apertures, with occasional communications, the apertures 

 from to \ inch apart, giving a perforated appearance to the whole area. In 

 horizontal sections they are seen as a system of longitudinal canals, with anas- 

 tomoses. In vertical longitudinal sections (Hexor to extensor aspect) they appear 

 fewer in number, some transverse but mainly longitudinal ; seeniingty none 

 vertical, as if the vessels did not enter from without, but on both surfaces 

 are seen a moderate number of apertures of considerable size. The channels 

 advance from the bone to the joint and are seen from the synovial surface as 

 dimples with a thin covering. These may readily be converted into and mis- 

 taken for apertures. They give the synovial area a mottled appearance. In 

 horizontal section through the middle of the carpus, the blood-channels are seen 

 throughout the great masses of cartilage, at distances of ^ to | inch apart, some 

 cut transversely, most cut obliquely, as if going in from the surface, with anas- 

 tomoses. On vertical section, not many are seen going in from the surface, but 

 on the surface itself a number of large apertures are seen. The blood-vessels of 

 the carpal cartilages must come from the surface, and the blood-channels within 

 the cartilages seem to form a system striking in vertically but forming an anas- 

 tomosing network. 



2 We make much of the fact of the epiphysis in man and various mammals 

 being distal on the metacarpal bones and proximal on the phalanges. I called 

 attention in 1863 (Edin. New Phil. Jour., July 1863) to the fact, with which 

 I had been long familiar, that in the cetacea there is an epiphysis at both ends of 

 each phalanx and also at both ends of each metacarpal bone. This epiphysis at 

 both ends of all these bones may be readily seen in an ossified condition in the 

 paddle of Globicephalus melas and of the common porpoise. But I have not 

 found it in an ossified condition in any whalebone whale, and Megaptera is no 

 exception to this. 



