x1 PHENOMENA OF ORGANIC NATURE 307 
useful to us in the performance of those services 
in which we employ him. 
And then, on separating and removing the whole 
of this skin and flesh, you have a great series 
of bones, hard structures, bound together with 
ligaments, and forming the skeleton which is 
represented here. 
Tn that skeleton there are a number of parts to 
berecognised. The long series of bones, beginning 
from the skull and ending in the tail, is called the 
‘spine, and those in front are the ribs; and then 
there are two pairs of limbs, one before and one 
‘behind ; and there are what we all know as the 
fore-legs and the hind-legs. If we pursue our 
researches into the interior of this animal, we find 
‘within the framework of the skeleton a great 
cavity, or rather, I should say, two great cavities, 
_—one cavity beginning in the skull and running 
through the neck-bones, along the spine, and 
ending in the tail, containing the brain and the 
‘Spinal marrow, which are extremely important 
organs. The second great cavity, commencing 
with the mouth, contains the gullet, the stomach, 
the long intestine, and all the rest of those internal 
apparatus which are essential for digestion; and 
then in the same great cavity, there are lodged the 
heart and all the great vessels going from it; and, 
besides that, the organs of respiration—the lungs: 
and then the kidneys, and the organs of repro- 
duction, and so on. Let us now endeavour to 
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