532 SCIENCE PROGRESS 



shows that children possess no tubercles at all. At about 

 fourteen years old the European jaw almost exactly resembles 

 that of the primitive races, while between fifteen and seventeen 

 years of age the prominences assume their fully developed 

 form. 



A very interesting piece of evidence comes from the 

 examination of deaf mutes. The writer has had great difficulties 

 in obtaining trustworthy information in this direction. The 

 one specimen in his possession of a French deaf mute of adult 

 age seems to show that when speech is absent the tubercles 

 do not develop at all, even in civilised races. It is interesting, 

 by the way, to note that the evidence seems to show that in 

 French and Italian jaws, and also in Irish, there is a fuller and 

 more uniform development in the genial tubercles than in the 

 average specimens found in our English museums. Possibly 

 this may be because these peoples speak their language with a 

 more painstaking articulation than is habitual in England. The 

 evidence tends to show that the tubercles are really not an 

 inevitable part of us, but that they are in each case a sign of 

 the activity of the muscle comparable to those rough ridges and 

 lines found on the bones in all muscular subjects. Such ridges 

 and roughenings have already been used as pieces of historical 

 evidence, for Rutimeyer in his researches among the remains 

 of prehistoric lake dwellings of Central Europe professed to be 

 able, by examining the bones, to differentiate between those of 

 wild animals which had led an active existence and those of 

 domestic animals which had lived a comparatively lazy life under 

 man's protection. 



Hence we possibly have in our genial tubercles an historic 

 record of the extent of which we have made use of articulate 

 speech. Moreover it seems to the writer quite possible that a 

 close and systematic examination of the arrangement of the 

 varying tubercles (for they do vary in a very strange manner) 

 in different races might give certain information as to the 

 characters of the languages spoken. We know how exceedingly 

 different are the muscular requirements for different languages, 

 since it is impossible, in many instances, for adults to so work 

 their tongues as to articulate an acquired language with anything 

 like correctness. 



The ethnological part of the writer's collection of casts of 

 jaws, although it contains specimens of nearly all families of the 



