602 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
part more than justified its continued existence by performing some 
function of vital importance to the species. 
Sir E. Ray Lankester, in one of his delightful scientific causeries, 
has pointed out that man’s chin consists of something more than a 
bony prominence on the jaw. There is a distinct fleshy pad upon its 
outer surface, which materially influences its outline and which con- 
sists of fatty tissue bound up in little cushionlike compartments 
almost exactly comparable to the pads on our fingers and toes. 
Although the esthetic and sex influences may be apparent here 
rather more than in the bony mandible itself—for who can gainsay 
the charm of a softly rounded chin?—the probable origin of this 
cushionlike covering is to be found in the fact that the protruding 
chin needed a pad for exactly the same reason as do a cricketer’s 
shins. It was into a world full of brutal tumult and hard knocks that 
the nascent chin first made its appearance. In the prize ring to-day 
it is a well-known fact that a blow on the chin is the most rapid way 
of putting your opponent hors de combat; and, moreover, it has 
become apparent that the nearer the exponent of ‘‘the nobie art” is 
in structure to a chimpanzee or gorilla the better chance will he have 
of wearing the glorious ‘‘echampion belt of all the world.” If we look 
at the bony structure of the chin in some of the prehistoric jaws we 
find it of astonishing strength, bemg stout and buttressed as if to 
stand terrific violence. This is remarkably shown in Emil Selenka’s 
admirable monograph on primitive jaws, published by Kreidel, of 
Wiesbaden, in 1903. From the above facts it seems reasonable to 
infer that man acquired such advantages as a chin can give at his 
peril; and here again it is suggested that some evolutionary need of 
exceptional potency molded man’s jawbone into its modern shape. 
It is when we turn a human mandible round and look at it from 
the inside and observe the surface beneath the central incisor teeth 
that we begin to get hints as to the actual functions of the chin and 
the causes which have led to our deviation from ancestral type. 
About halfway between the rim of the central tooth sockets and the 
lower edge there are to be found in practically all European and in 
most other jawbones two bony prominences known as the genial 
tubercles. (See fig. 18.) Below them are two somewhat similar 
prominences, generally much smaller (which often appear as faint 
convergent ridges), which are also known to anatomists as genial 
tubercles; but these, [ think, we need not consider of any importance 
in the present argument. They are to be found not only in the 
lowest savages and in prehistoric men but also in a large number of 
the apes and other vertebrates; indeed, I have detected apparent 
traces of them in those strange Permian reptiles of incalculable 
antiquity to which allusion was made above. They are the points 
