October 2, 1899.] 



KNOWLEDGE. 



219 



the reader how easily he recognises his own hat by the 

 accuracy of its fit. 



For descriptive purposes the long heads are called 

 dolichocephalic, the round head brachyeephalic. 



It is noteworthy that this peculiarity is not confined to 

 man. Of the anthropoid apes the gorilla and chimpanzee 

 are dolichocephalic, the orangs and gibbons brachyeephalic, 

 and it has been pointed out as an interesting coincidence, 

 if nothing more, that the racerf of men corresponding to 

 the geographicical distribution of these apes have the same 

 peculiarities of head form. But whilst much stress was 

 formerly laid on this difference in head form as a racial 

 characteristic, the trend of modern opinion seems to 

 be that too much reliance must not be placed on this 

 distinction. As we have said, the size, and to some extent 

 the form of the calvaria, depends on the development of 

 the brain, at the same time we hinted that the shape of 

 the brain case was to some extent correlated with the 

 masticatory apparatus, for in those cases where we have 

 large teeth and big jaws we necessarily require powerful 

 muscles to act upon them, and these by their size and 

 development necessarily react on the surfaces to which 

 they are attached. As a rule in brachyeephalic skulls the 

 fossfe for the attachment of the temporal muscles are low 

 and shallow, whereas in dolichocephalic skulls they are 

 high and deep. 



Another factor which determines the shape of the 

 calvaria must not be overlooked. As Virchow has pointed 

 out, the form of the skull depends to some extent on the 

 order in which the sutures or joints which unite the several 

 bones become closed, compensation always taking place in 

 the direction of the suture, thus if one of the longitudinal 

 sutures, the sagittal, for instance, becomes early synostosed 

 the skull tends to grow long and narrow ; if, on the other 

 hand, one of the transverse sutures becomes ossified the 

 skull can no longer increase in length, but expands trans- 

 versely, forming a round and broad head. Apart from the 

 question of heredity, which no doubt exercises a powerful 

 influence, any one of the foregoing causes may determine 

 remarkable individual variations of form. 



For scientific purposes these differences in shape are 

 recorded by the use of what is termed the cephalic index. 

 This expresses the proportion of the width of the skull to 

 its length, taking the latter as equivalent to one hundred ; 

 thus, supposing a "round" skull was strictly circular, its 

 width would be equal to its length, iu'., one hundred. On 

 the other hand, if the width of the skull was only half its 

 length, ('.(■., fifty, the form of the calvaria would be an 

 elongated oval, that is to say, long headed. Such extremes 

 as those above mentioned are not met with in practice, hut 

 the example stated may serve to illustrate the method. As 

 will be seen, this plan of grouping skulls is to some extent 

 a compromise, and is open to certain grave objections, ^\"e 

 assume that the length of the skull is the constant and the 

 width the variable, whereas we might with equal reason 

 adopt the transverse diameter of the skull as the constant 

 and the antero-posterior length as the variable. Further- 

 more, though the index expresses the proportion of the 

 width to the length, it by no means follows that it en- 

 ables us to map out with any accuracy the outline of the 

 skull ; it merely enables us to say that we could place the 

 skull within a cube the length and width of which corre- 

 spond to the proportions expressed by the index, just as if 

 we were making a box in which to pack the skull. The 

 accompanying diagram illustrates this ; both skulls have the 

 same cephalic index though their shape is entirely different. 



It will thus be seen that the cephalic index merely 

 indicates the proportion of width to length, and fails to 

 convey any accurate impression of contouring. Were we 



able to locate with precision the point of greatest width in 



relation to the length of the skull, the results would be 



more valuable, but unfortunately any such attempt would 



be beset with considerable difficulties. 



In practice, the cephalic index is obtained by the 



following formula : — 



Breadth x 100 ^ , ,. , , 



= Cephalic Index. 



Length 

 The results are grouped as follows 



: — Skulls with a 

 proportionate 

 width of eighty or 

 over are termed 

 Brachyeephalic. 

 This group in- 

 cludes, among 

 others, some Mon- 

 golians, Burmese, 

 American In- 

 dians, and Anda- 

 manese. 



Skulls of which 

 the index lies be- 

 tween seventy-five 

 and eighty are 

 Mcsaticephalic, 

 comprise Euro- 

 peans, Ancient 

 Egyptians, 

 Chinese, Ja- 

 panese, Polyne- 



Fia. 2 represents two Skulls liaving the sians, Bushliien, 

 same cephalie index — tIz., 79 — vet displaying o 

 very different forms. ' „ ., , , ,, 



•' Whilst skulls 



with a proportionate width below seventy-five are T'oUcho- 

 ccphalic, and are more or less typical of Veddahs, Eskimo 

 Australians, African Negroes, Kaffirs, Zulus, &c. 



The accompanying illustration shows three typical 



A. B. c. 



Fia. 3 shows examples of three varieties of Skidl form. A. Ex- 

 tremely dolichocephalic Skull of Vcddah, index 64; b. Mesaticephalic 

 Italian Skull, iudex 79; c, Brachyeephalic Swiss Skidl, index 88. 



examples of the variety of form characteristic of the three 

 groups above mentioned. 



♦ 



SIR MICHAEL FOSTER'S PRESIDENTIAL 

 ADDRESS TO THE BRITISH ASSOCIATION, 



September 13th, 1899. 



IN an address of singular literary grace. Sir Michael 

 Foster, at Dover, last month, reminded us that 

 some of the most fruitful advances effected in 

 chemistry, geology, and electricity, were made at 

 the very close of the eighteenth century, and that 

 the concrete achievements of the present are the transla,- 



