August i8, 1892] 



NATURE 



In the average well-developed Englishman with perfect teeth 

 the weight of the fleshy portion of the great jaw-muscles, 

 masseters and temporals, is 60 grammes, while the weight of 

 those as ascertained in two Australians was 74 grammes. 



Correlated with this greater musculature a sharper definition 

 of the areas for the attachments of the jaw-muscles is required. 

 The muscular fascicles are approximately of uniform size 

 in both microdonts and macrodonts, as the range of motion of 

 the jaw differs little in different races ; but when the skull is 

 smaller on account of the smaller size of the brain which it 

 contains, the temporal crest ascends higher on the side-wall. In 

 the average Englishman the temporal crests at their points of 

 greatest approximation anteriorly across the brows are 112 mm. 

 apart, but in the Australian they are only separated by 103 mm. : 

 the interstephanic distances in these two are respectively 132 

 and 114 mm. 



The more powerful stroke of the mandibular teeth upon the 

 anvil of the upper-jaw teeth in macrodonts renders necessarily a 

 proportionally stronger construction of the bases of support for 

 the upper alveolar arch. In any skull this arch requires to be 

 solidly connected to the wall of the brain-case to which the shock 

 of the impact is ultimately transmitted, and in order to protect 

 from pressure the delicate intervening organs of sight and smell, 

 the connection is accomplished by the reversed arches of the in- 

 fraorbital margins with their piers, malar and maxillary, founded 

 on the frontal angular processes. These foundations are tied 

 together by the strong supraorbital ridge, so that the whole 

 orbital edge is a ring, made up of the hardest and toughest bone 

 in the skeleton. 



A twofold modification of this arrangement is required in the 

 macrodont skull. The bony circum-orbital ring becomes 

 stronger, especially along its lateral piers ; and also as the 

 alveolar arch is longer, and consequently projects farther for- 

 ward, its basis of support must be extended to meet and bear the 

 malar and maxillary piers. But macrodonts are often micro- 

 cephalic, and therefore the frontal region of the skull must be 

 adjusted to form a foundation for this arch. In the average 

 English male skull, held with its visual axes horizontal, a per- 

 pendicular dropped from the anterior-surface of the fronto-nasal 

 suture will cut the plane of the alveolar arch between the premolar 

 teeth or through the first premolar. In an Australian skull the 

 perpendicular cuts the horizontal plane at the anterior border 

 of the first molar teeth. 



It is obvious, therefore, that to ensure firmness, the piers of 

 the arches must be obliquely set ; hence the jaw is prognathous, 

 but it is also needful that the supra-orbital arcade should be 

 advanced to meet and bear these piers, as the mandibular stroke 

 is always vertical. 



But the inner layer of the skull is moulded on the small frontal 

 lobes of the brain, so this forward extension must affect only the 

 much thicker and tougher outer table of the skull, which, at the 

 period of the second dentition, here separates from the inner 

 table, the interval becoming lined by an extension of the mucosa 

 of the anterior ethmoidal cell. In this way an air space, the 

 frontal sinus, is formed, whose development is thus directly 

 correlated to the two factors of brain development and size of 

 the teeth. If the frontal lobes are narrow in a macrodont skull, 

 then the foundations of the outer or malar piers of the orbital 

 arch must be extended outwards as well as forwards, the ex- 

 ternal angular process becoming a prominent abutment at the 

 end of a strong low-browed supraorbital arch, whose over- 

 hanging edge gives to the orbital aperture a diminished vertical 

 height. 



The crania of the two most macrodont races of mankind, 

 Australian and African, differ in the relation of the jaw to the 

 frontal bone. In the microcephalic Australian, the maxillae are 

 founded upon the under side of the shelf-like projection of the 

 outer table of the frontal, which juts out as a buttress to bear it. 

 On the other hand the nasal processes of the mesocephalic negro 

 ascend with greater obliquity to abut on the frontal, and have, 

 by their convergence, crushed the nasal bones together, and 

 caused their coalescence and diminution. 



The crania of the two most microcephalic races present dis- 

 tinctive features of contrast along the same lines. The Bush- 

 man's skull is usually orthognathous, with a straight forehead 

 and a shallow frontonasal recess, while the Australian skull is 

 [prognathous with heavy overhanging brows. These conditions 

 are correlated to the mesodontism of the Bushman and the 

 macrodontism of the Australian respectively. 



In the course of the examination of the relations of brain 



NO. IT 90, VOL. 46] 



development to skull growth, some interesting collateral points- 

 are elicited. The frontal bone grows from lateral sym- 

 metrical centres, which medially coalesce, union taking place 

 usually between the second and sixth years of age. It has been 

 noticed by anthropologists that metopism, as the anomalous 

 non-union of the halves of this bone has been termed, is rare 

 among microcephalic races, occurring only in about i per cent, 

 among Australian skulls. Increased growth of the frontal lobes 

 as the physical accompaniment of increased intellectual activity 

 interposes an obstacle to the easy closure of this median suture, 

 and so in such races as the ancient Egyptian, with a broader 

 forehead, metopism becomes commoner, rising to 7 per cent. 

 In modern civilised races the percentage ranges from 5 to 10. 

 In following out the details of this enumeration, I have spoken 

 as if the raicrodontal condition had been the primary one, 

 whereas all the available evidence leads to show that the contrary 

 was the case. The characters of all the early crania. Neander- 

 thal Engis, and Cromagnon, are those of macrodonts. The 

 progress has been from the macrodont to the microdont, as 

 it probably was from the microcephalic to the macrocephalic. 



The effects of the variations in size of the teeth are nume- 

 rous and far-reaching. The fluctuation in the weight of the 

 jaw depending on these variations has an important influence 

 on the centre of gravity of the head, and affects the set of 

 the skull on the vertebral column. This leads to a conse- 

 quent change in the axes of the occipital condyles, and it is 

 one of the factors which determines the size of the neck- 

 muscles, and therefore the degree of prominence of the nuchal 

 crests and mastoid process. 



As the teeth and alveolar arches constitute a part of the appa- 

 ratus for articulate speech, so these varieties in dental develop- 

 ment are not without considerable influence on the nature of the 

 sound produced. The necessarily larger alveolar arch of the 

 macrodont is hypseloid or elliptical, more especially when it has 

 to be supported on a narrow frontal region, and this is asso- 

 ciated with a more extensive and flatter palatine surface. This, 

 in turn, alters the shape of the mouth cavity, and is associated 

 with a wide flat tongue, whose shape participates in the change 

 of form of the cavity of which it is the floor. The musculature 

 of the tongue varies with its shape and its motions, upon which 

 articular speech depends, become correspondingly modified. 

 For example, the production of the sharp sibilant S requires the 

 approximation of the raised flexible edge of the tongue to the 

 inner margins of the teeth behind the canines, and to the pala-' 

 tine margin close behind the roots of the canine -and lateral 

 incisor teeth. This closes the vocal tube laterally, and leaves a 

 small lacuna about 5 mm. wide anterially, through which the 

 vibrating current of air is forced. A narrow strip of the palate 

 behind the medial halves of the median incisors bounds this 

 lacuna above, and the slightly concave raised tongue-tip limits 

 it below. 



With the macrodont alveolar arch, and the correspondingly 

 modified tongue, sibilation is a difficult feat to accomplish, and 

 hence the sibilant sounds are practically unknown in all the 

 Australian dialects. 



It is worthy of note that the five sets of muscular fibres, whose 

 function it is to close laterally the flask-like air-space between 

 the tongue and the palate, are much less distinct and smaller in 

 the tongues of the Australians which I have examined than in 

 the tongues of ordinary Europeans. 



There is a wide field open to the anatomical anthropologist in. 

 this investigation of the physical basis of dialect. It is one 

 which requires minute and careful work, but it will repay anj^ 

 student who can obtain the material, and who takes time and 

 opportunity to follow it out. The anatomical side of phonology 

 is yet an imperfectly known subject, if one may judge by the 

 crudeness of the descriptions of the mechanism of the several 

 sounds to be found even in the most recent textbooks. As a 

 preliminary step in this direction we are in urgent need of an 

 appropriate nomenclature and an accurate description of the 

 muscular fibres of the tongue. The importance of such a work 

 can be estimated when we remember that there is not one of the 

 260 possible consonantal sounds known to the phonologist which 

 is not capable of expression in terms of lingual, labial, and 

 palatine musculature. 



The acquisition of articulate speech became possible to man 

 only when his alveolar arch and palatine area became 

 shortened and widened, and when his tongue, by its accom- 

 modation to the modified mouth, became shorter and more 

 horizontally flattened, and the higher refinements of pronuncia- 



