VERTEBRATED TYPE OF STRUCTURE. 
85 
u bi-lateral symmetry ” extends to the arrangement of those 
internal parts which are connected with the functions of 
animal life; namely, the nervous system, the organs of sense, 
and the muscular apparatus. But it does not always extend 
to the organs of nutrition, which are unequally disposed on 
the two sides : thus, in Man, the heart and stomach are on the 
left side, and the liver on the right, while the lungs are much 
larger on the right side than on the left. But in many of the 
lower Yertebrata, there is an almost perfect symmetry in the 
disposition of these organs, as there is also in the early embryo 
of those in which this symmetry is subsequently departed 
from; so that it may be truly said that this symmetry is cha¬ 
racteristic of the Vertebrate type, although for special purposes 
it is frequently superseded. 
Fig. 25.— Skeleton of the Ostrich. 
71. In all Yertebrated animals, the skeleton is chiefly 
internal (fig. 25); and consists of bones, which are capable of 
