THE MACAQUES. 
115 
Guenons; moreover, most of them have throat or laryngeal sacs, which open into the membrane 
above the vocal organ and below the base of the tongue (in the thyroid membrane). 
On examining their jaws it will be noticed that there is the same number of teeth as in the other 
Monkeys already described, and that the upper eye or canine tooth on each side is very strong and 
long. Now, these teeth are not for killing or stopping living prey, although them possessors do not 
hesitate to snap up a good-sized Beetle, a small Lizard, or even a Frog, but they make, with the first 
false grinder of the lower jaw, a capital nut-opener. The canine, when the mouth is shut, fits just in 
front of this tooth, which is usually called the first pre-molar, and which is pressed back and made to 
slant in the jaw by the constant pressure and movements of the canine. The back of the canine is 
sharp, and comes in contact with the equally sharp edge of the slanted pre-molar below, so that when a 
nut comes between the two it is cut and crushed at the same time. The canine does not thus fit into a 
diastema, or vacant space, but is of great use to the animal. This arrangement is interesting, because it 
produces a distortion of the front back teeth of the lo wer jaw for a definite and useful purpose : it is 
noticed in some of the Guenons, and is particularly seen in mouths of the great Baboons, which will be 
noticed further on. 
The other back teeth resemble somewhat those of the Guenons, but the last one of the lower jaw 
has five cusps, or prominences, on it. 
All these Monkeys going very readily on all-fours have several interesting modifications of the 
structures observed in the climbing Monkeys, but of course their general construction is the same. 
They have not, however, the pouched stomachs of the Semnopithecus, and their nearest resemblance is 
to the African Guenons. 
Like in all the Monkeys which are lower in the animal scale than the great man-shaped Apes, 
the Macaques have narrow wrists, long finger-bones, and a short and backwardly-placed thumb. 
There are nine bones in the wrist. The hip- and liaunch-bones are long, and the first are hollowed 
out, and their direction refers to the method of progression on all-fours, and their general appearance 
is rather that noticed in the regular four-footed beast of prey, and they differ much in breadth 
relatively to those of man. 
The length of the tail depends upon the number of the tail-pieces, or vertebrae, and upon their 
size. In the Gibraltar Ape there are only three of these caudal vertebrae, but in the Bhunder there 
are fifteen and sometimes eighteen in the tail, which measures nine inches, whilst in the Pig-tailed 
Inuus there are seventeen. It appears that some of the long-tailed kinds have no more vertebrae 
than the others, but that the diminished length is due to their shortening. The long and middle-sized 
tailed kinds have chevron or Y-shaped bones under the tail, and the nature of these has been 
explained already. 
Living upon a great variety of food, and using their jaws with rapidity, these Monkeys are 
furnished with a curious modification of a muscle, which exists in man and the higher Apes. There 
is in these a muscle on either side of the throat, which draws the chin down, or, in other words, helps 
to open the mouth. It is called the two-bellied, or digastricus muscle, as it has two muscular masses — 
one attached to the lower jaw, and the other to the lump of bone behind the ear — and they are united 
by a thin tendon. This tendon is attached to the side of the bone at the base of the tongue, or 
os hyoides, and it passes through a loop of a muscle which passes from the ear-bone (styloid process) to 
the os hyoides. The muscle acts as follows : — When the mouth is to be opened after swallowing, the 
base of the tongue-bone is pulled down by a muscle which comes from the breast-bone to it, and then the 
front belly, or muscle of the digastricus, pulls from the base of the tongue against the lower jaw and 
drags it open. But when the muscle relaxes, and the jaw is shut preparatory to swallowing, the 
digastricus begins to assist in this operation. In swallowing, the base of the tongue is drawn upwards 
towards the roof of the mouth, and the back and front bellies of the muscle now under consideration 
drag on their fixed tendon, and straighten, so as to assist in this. 
In the Macaques, this tendon is replaced by muscular bands, and greater vigour is given to the 
muscle, so that the jaw is pulled at more rapidly, and the tongue is elevated with energy. 
As there is a greater power given in drawing up the tongue in the first stage of swallowing, there 
must be something extra to pull it down again in the second stage, for in this the back of the throat, 
the gullet, and the back of the tongue are all brought from above to a lower level. This is arranged 
