180 
HISTOLOGY OF ANIMALS, 
glottis of the human subject, as shown at c, and in the 
auricles of the ear of the larger mammalia. In these 
situations, the cells are readily separated from the matrix ; 
indeed, they often drop out, and leave the fibrous frame- 
work entire. 
Fibro-cartilage is not so prone to ossification as the 
simple fibrous structures ; for in two examples of anchy- 
losis of the vertebrae, selected from a large number in 
the Museum, the discs have, in each case, disappeared, 
and the ossific matter is confined to the fibrous tissue, 
or anterior common ligament, which binds them firmly 
together; in some instances, the space originally filled 
by the disc is still present, but remains unoccupied by 
bone. A striking specimen, illustrative of this fact, is 
represented in Fig. 138,b. In the two upper vertebrae, 
the ligament has become ossified, and a considerable 
quantity of bone has been formed, so as to cover the 
anterior part of the inter- vertebral space ; there is, 
however, no junction between the two vertebrae, but 
between the second and third the union is complete, 
and in both cases, the space originally occupied by the 
inter-vertebral disc is empty. This fact is quite as 
evident in the spine of the lower orders of mammalia 
as in man, and is very common in the Horse and 
Sheep. 
