CHA Pacis. y-1f. 
A BIRD’S OUTER WRAP. 
Tue skin is the primary outer garment of every 
animal. It is more than this. It is a very important 
excretory organ, “the largest gland in the body.” 
Besides this, it assists the lungs in reptiles and others 
in oxidizing the blood. To the lowest creatures it is 
lungs, stomachs, legs and tentacles, with perhaps 
other functions. 
But it has been more than this. It has been the 
source to all organisms of their greatest progress. 
Every class of creatures has moved by it, every form 
of motion has employed it—swimming, crawling, walk- 
ing, climbing, flyng—from protozo6dn to mammal. 
Perhaps, as we have seen, the bird itself first flew 
directly by means of it. 
But it has been more than this even. It has been 
the great builder of other parts of the body. From 
the waste of lime it shaped the shell of the mollusc, 
and formed of chitin the outside skeletons of the crus- 
taceans and insects. While it is not demonstrated 
that the backbone had a dermal origin, as it may, we 
know the appendicular skeleton of toes and limbs had 
its origin in skin folds and sank inward to meet the 
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