340 MR. J. B. SUTTON ON THE INTERVERTEBRAL [June 29, 
body and two additional centres for the epiphysial plates, as in other 
regions of the spine. When the segments of the sacrum commence 
to ankylose, the adjacent epiphysial plates fuse with each other 
before they join the bodies of the vertebree to which they belong. 
This fusion of epiphyses is of a deceptive character, for it does not 
occur throughout the whole width of these bony menisci, but only 
around their circumferences. Hence if a section be carried through 
the sacrum, a piece of cartilage may be detected situated in a central 
cavity, the boundaries of which are constituted by the epiphysial 
plates; this piece of cartilage persists long after the various seg- 
ments of the sacrum have, from all external evidence, become 
Fig. 3. 
A section through the human sacrum, showing the epiphysial plates uniting 
with each other peripherally before fusing with their centra. 
firmly united. This remarkable arrangement of the epiphysial plates 
is represented in fig. 3. 
It is quite possible that this mode of fusion is applicable to the 
cervical vertebrze of Whales; for an examination of this region of the 
column in a young Porpoise shows well-marked indications of 
peripheral union of the epiphysial plates, whilst they are still 
separate from the bodies of the vertebrae to which they respectively 
belong. My attention was first drawn to this question when 
examining the sacral vertebree of a young skeleton of the Great 
Anteater, Myrmecophaga jubata. After the skeleton had been 
macerated, the sacrum broke up into its component elements, the 
epiphysial plates separated from the vertebra, but the contiguous 
plates were firmly united in pairs. 
So far as my observations on other mammals have extended, this 
mode of fusion appears to be general. 
There are other points in the axis which demand some notice. 1 
was unaware, until reading Prof. Cunningham’s paper, that any 
