538 
MAMMALIA. 
in order to obtain tbe spark that is to produce beat and light, 
thus acting as a Man. 
Another characteristic which removes every doubt as to the 
place to be assigned to Monkeys in the zoological scale, is the 
gradual impairment of their faculties as they advance in years — 
an impairment which corresponds to a growing depression in the 
anterior part of the brain, to the elongation of the face, and to a 
considerable diminution of the facial angle.* However submissive 
and obedient they may have been previously, in old age they 
become vicious, quarrelsome, and averse to the habits of their 
younger days ; everything indicates a closer approach to the con- 
dition of a veritable brute, from which at first they appeared to be 
separated. It is worthy of notice that if these animals in their 
early days have exhibited a more sociable disposition, and a greater 
facility to assimilate themselves to the acts and gestures of Man, 
they afterwards degenerate more rapidly. Thus it is that, con- 
trary to what occurs with mankind, the progress of age brings to 
the Monkey the decadence of that intelligence and the abolition 
of those qualities with which it is endowed at birth. 
We need not carry the parallel between Man and the Monkey 
any further, for the first is so far beyond comparison superior to 
the second, that no tie of relationship connects them together. 
Therefore, without more delay, we will point out the general 
characteristics of the Quadrumana, and the divisions which 
naturalists have sub-divided them into. 
Although we have said that the distinctive trait of the Quadru- 
mana is their being provided with four hands, this, however, is 
not strictly correct. Some species are more or less deficient in a 
thumb on the anterior members. Such are the Colobes, Ateles, 
and the Eriodes. Others, such as the Ouistitis, and the majority 
of the Makis, are furnished with five regular fingers, but do not 
have the thumb opposable except in the posterior limbs. What- 
ever the nature of these exceptions may be, the character drawn 
from the number of hands remains sufficiently marked for us to 
* The facial angle is that which results from the meeting of two straight lines, 
one drawn from the auditory meatus to the root of the nose, the other at a tangent 
to the base of the forehead and the most prominent part of the upper jaw. The 
naturalist Camper was the first to make known this practical method of measuring 
approximately the intellectual capacity of an individual. According to him, the 
facial angle is open in proportion as the intelligence of the subject is developed. 
