122 PROFESSOR STRUTHERS. 



the height is very nearly the same in both. The high-up com- 

 mencement of the lower border of the transverse process gives a 

 longer neck to the pedicle in Megaptera, and the inward slope 

 of that border towards the body increases the upward and out- 

 ward obliquity of the pedicle in Megaptera. That obliquity is 

 related to the more outward position of the articular processes 

 in Megaptera. 



Spinal Canal in the Neck. — (a) Capacity. — The increase in 

 height, with diminution in width of the canal at the 3rd ver- 

 tebra, as compared with the 4th, in both Megaptera and B, 

 musculus, is a transition to the form in the axis, in which the 

 height is considerably increased and the width diminished. In 

 height the canal increases a little backwards from the 4th to 

 the 7th (3| inches to 3|), after which the increase to the dorsal 

 height begins (1st dorsal, 3| inches). The ividth is greatest at 

 the 6th and 7th cervical (7 inches) and 1st dorsal (6| inches), 

 and thence diminishes forwards to Qh inches on the 4th, and 

 backwards along the rest of the column. 



[In B. 7nuscidus, the height from the 4th to the 7th cervical (2f 

 inches) is less than in Megaptera (1st doi-sal, 3 inches). The width, 

 from the 4th to the 7th cervical, increases from 6f inches to 7 ; is 7^^ 

 on the 1st dorsal, and thence diminishes backwards.^] 



(b) Form. — The somewhat higher arch in Megaptera is not 

 obtained by greater slope of the lamina towards the spine, but 

 rather by the lateral angles being carried higher up, and there- 

 fore less sharp than in B. musculus. In the floor of the canal 

 the longitudinal median ridge of the bodies is seen in B. miis- 

 culus, extending all along the neck. It begins near the fore 



^ The most capacious part of the spinal canal being in both the back part of 

 the neck, would accord with an assumed enlargement of the spinal cord at the 

 origin of the nerves of the pectoral fin. If so, the enlargement should be greater 

 in Megaptera with its enormous pectoral fin. The bony canal here is more 

 capacious in Megaptera, but only from its greater height. In the measurements 

 of the three previously noted series of cervical vertebrre of B. musculus {loc. cif., 

 1872, Table, p. 20) the capacity of the canal of the 6th and 7th was found not to 

 be greater than at the 4th and 5th cervical. In one it was greatest at the 5th 

 and 6th; in a second at the 4th and 5th; in the third, at the 6th and 7th. But 

 considering the small size of the spinal cord (at the middle of the neck the tube 

 of dura mater was found to be only 1 inch in diameter {loc. cit., 1872, p. 5), and 

 that the great part of the bony canal is occupied by rete mirabile, correspondence 

 between any special enlargement of the cord and the capacity of the bony canal 

 can hardly be expected. 



