MOLLITIES OSSIUM. 
175 
of a scale of the Bony Pike , of North America, Lepi- 
dosteus osseus , Fig. 136. 
In Mollities ossium , there is a deficiency of the 
earthy constituent of the bone. The change first begins 
in the lucanae, which become larger and larger, and 
the bone around them more and more transparent; 
finally, several lacunae unite to form one cavity, which, 
however, does not long remain empty, but is occupied 
by a soft kind of adipose tissue, so that such bones are 
always extremely thin and full of fat. For this reason 
Mollities ossium may be considered as an example of 
the fatty degeneration of bone. 
The last form of cartilage which I shall mention is of 
a very peculiar character, being always more or less 
tubular. It is found in the vertebrae of the Vaagmaer 
or Riband-fish, — a specimen of which, about three 
years since, was captured off St. Andrews. For our 
knowledge of this interesting structure we are indebted 
to the late Dr. John Reid ; and the account of the 
anatomy of the fish was the last contribution to science 
made by that distinguished anatomist. A transverse 
section of one of the vertebrae, is illustrated at b, in 
Fig. 137. It exhibits four different structures: the 
first is an outer coating of dense areolar tissue ; the 
second occupies the centre, and consists of a gela- 
tinous substance somewhat resembling simple carti- 
lage ; the third composes the radii, which extend from 
the centre to the circumference ; whilst the fourth con- 
sists of a firm fibrous structure, occupying all the 
