408 Canadian Record of Science. 



is partial and his explanation inadequate. Both these wri- 

 ters have indicated the direction in which the truth lies, but 

 neither gets at it wholly, as I shall now endeavour to show. 



That Mr. Eaton is correct in believing that exposure of 

 the body to the sun and air has something to do with hair 

 production, any man may prove to his own satisfaction by 

 leaving his arms or other portions of his body uncovered 

 much more than usual, during a holiday season at the sea- 

 side or in the country. But Mr. Eaton states the case alto- 

 gether too strongly for the influence of heredity. The 

 degree to which such peculiarities as baldness are inherit- 

 ed is one of the most disputed matters ; though unques- 

 tionably something must be allowed to such tendency, 

 perhaps a good deal. 



There can be no doubt that the loss of hair and of teeth 

 prematurely are related in fact. Have such losses a com- 

 mon cause? Mr. Eaton's explanation is disuse. Professor 

 Cope would explain the fact stated by dentists, that the 

 last molar (wisdom) tooth and the lateral incisor of the 

 upper jaw frequently do not appear, by what he calls 

 " retardation" of the growth of the jaws, and to succes- 

 sively prolonged delay in the appearance of the teeth • 

 while these again are related to an enlargement of the 

 upper part of the head and of the brain. Is it not possible 

 that all of these causes and perhaps others may combine 

 to effect this result ? 



Taking up the case against the stiff hat, Mr. G-ouinlock 

 explains how readily the arteries can be compressed, especi- 

 ally when the hair is cropped close; he thinks the fact 

 that below the line of pressure the hair remains, while it 

 disappears above it, is quite clear upon his theory; and to 

 account for the presence of hair over the temporal region 

 when absent on the crown, he insists that here the temporal 

 muscle acts as a cushion, preventing pressure. But this 

 writer seems to forget that there are superficial and middle 

 temporal arterial branches as well as deep ones, and that it 

 is just these superficial ones (liable to pressure) that have 

 most to do with supplying blood to the hair bulbs. He 

 also takes no account of other methods besides pressure by 



