SCHULTE, SEI WHALE. 485 



In all of the bodies except the last five, a center of ossification is present. These in section 

 are oval as far as the midthoracic region, beyond this circular. In the terminal vertebrae the 

 cartilage has begun to calcify except in the last two. 



The spinal cord extends to the level of the thirty-second vertebra, beyond which it is con- 

 tinued as the filum terminale surrounded by the nerves of the cauda equina. The neural arch is 

 lacking in the last ten vertebras, and in the seven or eight vertebrae rostral to these it was of minute 

 dimensions. 



The intervertebral disks are in general biconcave, expanding towards the periphery of the 

 centra and very thin in the middle. The width of the expanded circumference increases caudad, 

 being greater opposite the larger chevron bones. At the end of the series it diminishes rapidly. 

 A few of the disks of the upper thoracic region departed slightly from this simple type showing a 

 small lenticular thickening in their centers. 



The chevron bones are ten, possibly eleven in number, the last being so minute a nodule in 

 the dense fibrous tissue of the region that I am not sure it was cartilage. No joint was present 

 between it and the corresponding intervertebral disk as in the case of the other ten. The second 

 is the longest of the series; the last three or four are very small. The first articulates with the 

 disk between the thirty-sixth and thirty-seventh vertebra. 



Cervical vertebrce. These vertebrae have the compressed bodies and large hoop-like transverse 

 processes of the adult, with the exception of the first in which the transverse process is reduced 

 to a tubercle, and of the second where it is a large plate perforated by a rather small foramen. 

 These processes converge by their tips, in consequence of the inclination of those of the second 

 and third vertebrae. The inclined and enlarged transverse process of the axis overhangs that 

 of the third vertebra, its tip lying opposite the interval between the transverse processes of the 

 third and fourth, but not descending actually to the level of the latter vertebra. The process 

 of the fourth cervical is transverse as is also that of the fifth. In comparison with B. musculus 

 ( = physeter) 1 , there is much less convergence of these processes, and the lower ones of the series 

 do not ascend as in that species, in consequence of which a somewhat greater range of move- 

 ment in the neck may perhaps be inferred of B. borealis. 



The costal process of the sixth cervical vertebra is reduced to a small nodule of cartilage, 

 which is not fused with the centrum, but articulates with it, and within a narrow range is mov- 

 able upon it. The condition is symmetrical. The seventh cervical vertebra has lost its costal 

 process. This is now represented by the upper bar of the so-called bicipital rib. That we are 

 dealing here with a structure analogous to the variant cervical rib of man seems certain. The 

 element in this foetus would seem to represent the distal portion of the rib beyond its tubercle, 

 for it is connected by ligament to the true transverse process of the seventh cervical. The 

 proximal portion, the neck and head, are absent. 



It is possible to find in the great size of the vertebral plexus a factor in the interruption 

 of the costal processes of the last two cervical vertebrae. This large plexus has expanded in the 

 foramina transversaria of the third, fourth and fifth vertebrae, reducing the transverse processes 

 to slender bars of cartilage. That this may be a real factor in the modification of these parts 

 and not simply a correlated peculiarity, is borne out by the well known phenomenon of absorption 

 of cartilage or bone under pressure from blood vessels. At the root of the neck, the vertebral 



1 Struthers, J. On the cervical vertebrae and their articulations in fin-whales. Jour. Anat. and Phys., Vol. VII, 1872. 



