70 STRUCTURE AND COMPARISON. 



which, not being needed, do not develop. The only name we 

 need to learn here is carpus, the scientific name for the wrist, 

 whether in man, birds, or mammals. As this is sometimes 

 marked by a band of bright color, books on birds sometimes 

 speak of the carpus, or carpal joints, or the " bend of the 

 wing," as being brown or yellow. 



Next, let us turn to the breast- and shoulder-bones. We have 

 a breast-bone, a little straight slip of a bone that we cannot 

 feel distinctly, but it has no ridge down the centre like the 

 great keel of the chicken's breast-bone, for we have not the 

 heavy muscles that need such a bone to support them. Do we 

 have a wish-bone ? Yes, or something that corresponds. Our 

 two collar-bones do the same work as the chicken's wish-bone, 

 in bracing the shoulder out. Perhaps some of you may re- 

 member what happens to the arm when the collar-bone is 

 broken. Did you ever notice the differences in wish-bones? 

 Collect a few of different game birds and see how they brace 

 the shoulder in different ways. The bird has shoulder blades, 

 much longer and narrower than our own ; and, in addition, he 

 has " shoulder blades in front," the coracoids, those flat, 

 wide, straight bones that are braced against the top of the 

 keel to hold the shoulder up and out. Study the relation of 

 these bones as they lie on the carcass of the fowl, and you 

 will see how much it reminds you of the rowlock of a racing 

 scull, heavily braced far out from the side of the boat, so as to 

 give a greater purchase to the oar. By means of this tripod 

 of bones the shoulder is held far enough out from the centre 

 of the body for the muscles to get a good purchase. 



We see that while the larger bones of a bird are about the 

 same as our own in number, they are different in shape and 

 proportions. Now we are ready to go 011 and learn how they 

 are fitted to the life the bird leads and how he swims and flies. 



