178 
HISTOLOGY OF ANIMALS. 
the body is subjected. In the Cetacea the discs are 
of immense size ; and the articular surfaces of the 
vertebrae in many of these animals not being anchylosed 
to the bodies, may also be found detached as discs. 
These last are smooth and a little concave on their 
articular surface, convex and rough on their epiphysal ; I 
remember when I first became connected with this 
College, that the late Mr. Clift told me he once 
met with a specimen about three or four inches in 
diameter, in the shop of a dealer in curiosities in the 
Strand, who gravely informed him more than once that 
he valued it above everything in his shop, as he con- 
sidered it a most rare and beautiful example of a fossil 
crumpet, which it much resembles in appearance. 
These discs are very abundant on the sea-shore in 
northern climates ; and when Her Majesty’s ship Hecla 
was wrecked, I was informed by one of the officers, that 
they served the crew 7 of that unfortunate vessel as plates. 
The discs of fihro-cartilage between these vertebrae are 
often more than two inches thick. Masses of fibro- 
cartilage exist in certain joints, under the name of inter- 
articular fibro-cartilages. We have examples in the 
temporo-maxillary and sterno-clavicular articulations of 
the human subject. When either of these is divided 
transversely, and a section made sufficiently thin for 
examination by the microscope, it will be found that it 
is composed chiefly of a net-work of fibres, within which 
a few cartilage cells are enclosed. 
The cells, Fig. 138, A, are large and tolerably 
