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NATURE 
259 
portant in man, enters largely into the composition of the 
teeth in many of the lower animals, The statement 
~ advanced by Jean Jacques Rousseau, on the one hand, 
that man is a herbivorous animal, and by Helvetius on the 
other, to the effect that he is carnivorous, both seem to be 
refuted by the general characters of the teeth, so far as any 
evidence can be derived from such a source ; for in this 
“point of structure man occupies an intermediate position 
between the Carnivora and the Herbivora, and appears 
to be adapted for the consumption of both animal and 
vegetable substances, though doubtless life can be well 
preserved with a due selection and sufficient supply of 
either, as we shall subsequently see. 
The lining of the mouth is a mucous membrane of con- 
siderable thickness, containing numerous glands, and 
covered with many tiers of tesselated epithelial cells, 
into the deep surface of which sensitive and vascular 
papillze from the membrane itself project. 
The movements of the lower upon the stationary upper 
jaw in man are effected by the muscles, exhibited in 
Figs. 2 and 3. 
They comprise vertical, lateral, and backward and for- 
ward movements. The depression of the lower jaw is 
accomplished with considerable rapidity by the contrac- 
tion of three or four small muscles—the digastric, stylo- 
genio, and mylo-hyoid—forming the floor of the mouth, 
the first-named being the principal agent in the Carnivora. 
Fic. 3.—View of the internal muscles of mastication. A, zz¢érnad pterygoid 
muscle; B, externa/ pterygoid muscle, 
From the position of the joint or pivot on which the lower 
jaw moves, the front teeth can be nearly twice as widely 
separated from one another as the back. The difference 
-in the gape of the jaws varies in different people, and to a 
greater extent than might at first sight be supposed. In 
some measurements that I have made, I find that whilst 
the distance between the free borders of the front teeth 
does not, in some instances, exceed one inch, in others it 
amounts to upwards of two inches. The segment of a 
circle formed by the upper is usually somewhat larger 
than that of the lower jaw. Its elevation, which is a 
far more energetic movement, is performed by the tem- 
poral (A, Fig. 2), masseter (C, D, Fig. 2), and internal 
pterygoid muscles (A, Fig. 3). All these muscles are 
attached to the jaw between the fulcrum or condyle 
of the jaw, shown in Fig. 2, just in front of the ex- 
ternal opening of the ear, and the weight to be moved 
or fore-part of the jaw. They therefore constitute 
levers of the third order; and hence, though acting 
promptly, are placed at a comparative disadvantage 
for exerting their fullest force. Still their power is im- 
mense even in man, who is again surpassed by many of 
the Carnivora. It is not easy to estimate it. I have 
endeavoured to do so, however, by ascertaining the pres- 
sure required to crush a Brazil-nut, which seems to be 
about the limit of the power possessed by young people 
with good teeth, At least very few can crush the stone of 
the peach. I find that a weight of about 84lb., but 
varying from 56lb. to 1oolb. is requisite to break a Brazil- 
nut when placed on one of its flat sides, and this probably 
is not a very unfair representation of the average power 
of the three above-mentioned muscles. The lateral move- 
ments of the lower jaw are effected by the alternate con- 
traction of the external pterygoids (B, Fig. 3), which are 
consequently seen in their highest state of development 
in the Ruminants. They are feeble in man. The for- 
ward and backward movements, also feeble, are due, the 
former to the external pterygoids, the latter to the deep 
portion of the masseter (Cc, Fig. 2), the posterior fibres of 
the temporal and the internal pterygoid. 
Another muscle deserves to be noticed—the buccinator 
—which forms a considerable proportion of the thickness 
of the cheek, and which is an important agent in pre- 
venting the accumulation of food between the teeth and 
the cheek, the occurrence of which is so troublesome in 
some cases of paralysis. It is remarkable that all these 
muscles are supplied by one and the same nerve, the fifth ; 
the last-named, however, receiving some additional motor 
filaments from the seventh or portiodura. 
The movements of the tongue, which are under the 
influence of the hypoglossal nerve, are of very great 
importance also in aiding mastication, since its wonderful 
tactile sensibility enables us to feel for and thrust back 
between the teeth portions of food which have escaped 
their action, The centre for co-ordinating the various 
movements required for mastication appears to be situated 
in the medulla oblongata. 
Having thus considered the mechanical process to 
which the food is subjected in the mouth, we shall proceed 
in another article to consider the chemical changes 
effected in it by the act of insalivation. H. POWER 
NOTES 
WE have more than once had to notice the liveliness recently 
exhibited by science at the Antipodes, This has now found 
expression in the issue of a monthly journal in Australia called 
“«The Scientific Australian,” a journal of industry and instruc- 
tion, specially devoted to those engaged in scientific, artistic, and 
industrial pursuits, and to the promotion of technological educa- 
tion amongst the operative classes. The editor, Mr. J. S. Knight, 
Assoc. Inst. C.E., F.R.I.B.A., appears to have enlisted the 
services of the most eminent scientific men, not only in Victoria, 
but in the sister colonies of New South Wales, Queensland, South 
Australia, Western Australia, Tasmania, and New Zealand, and 
the articles, as a general rule, are to be signed. It is gratifying 
to find these signs of life in our colonies ; we shall watch with 
interest the career of our contemporary, the first number of which 
was to be published at Melbourne on the Ist of the current 
month, and wish it every success. 
AT the public sitting of the Paris Academy of Sciences, held 
on the 11th inst., the following prizes were awarded :—‘“‘ The 
Astronomical Prize, Lalande foundation, to Mr. J. Watson, for 
the discovery of eight new asteroids in one year. The Mechanical 
Prize, Monthyon foundation, to M. Arson, for his experimental 
researches on the flow of gases in long conduits. Statistical Prize, 
Monthyon foundation, to M. Chenu, for his medico-chirurgical 
statistics of the Italian campaign of 1859-60. Prize established 
by the Marchioness Laplace, to M. F. A. Voisin. Trémont 
Prize to M, Le Roux, to aid and encourage him in the pursuit of 
researches on the index of refraction for certain vapours, and on 
the measurement of the heat developed by electric currents. 
Poncelet Prize to M. J. R. Mayer, of Heilbronn, for his memoirs 
on the mechanical theory of heat; Prize for Medicine and 
Surgery : a medal of the value of 3,000 francs, to MM. Legros 
and Onimus, for their works on the application of electricity to 
therapeutics ; a medal of the value of 2,000 franes to M. Cyon, 
