The everyday functions of the human body are practically the same as
those of the anthropoid ape, and similar disorders are common to both.
Monkeys may be infected with certain microbes to which man is peculiarly
liable, such as the bacillus of tuberculosis. Darwin showed that various
human gestures and facial expressions have their counterparts in
monkeys. The sneering curl of the upper lip, which tends to expose the
canine tooth, is a case in point, though it may be seen in many other
mammals besides monkeys--in dogs, for instance, which are at some
considerable distance from the simian branch to which man's ancestors
belonged.
When human blood is transfused into a dog or even a monkey, it behaves
in a hostile way to the other blood, bringing about a destruction of the
red blood corpuscles. But when it is transfused into a chimpanzee there
is an harmonious mingling of the two. This is a very literal
demonstration of man's blood-relationship with the higher apes. But
there is a finer form of the same experiment. When the blood-fluid (or
serum) of a rabbit, which has had human blood injected into it, is
mingled with human blood, it forms a cloudy precipitate. It forms almost
as marked a precipitate when it is mingled with the blood of an
anthropoid ape. But when it is mingled with the blood of an American
monkey there is only a slight clouding after a considerable time and
no actual precipitate. When it is added to the blood of one of the
distantly related "half-monkeys" or lemurs there is no reaction or only
a very weak one. With the blood of mammals off the simian line
altogether there is no reaction at all. Thus, as a distinguished
anthropologist, Professor Schwalbe, has said: "We have in this not only
a proof of the literal blood-relationship between man and apes, but the
degree of relationship with the different main groups of apes can be
determined beyond possibility of mistake." We can imagine how this
modern line of experiment would have delighted Darwin.
[Illustration: THE GORILLA, INHABITING THE FOREST TRACT OF THE GABOON IN
AFRICA
A full-grown individual stands about 5 feet high. The gait is shuffling,
the strength enormous, the diet mainly vegetarian, the temper rather
ferocious.]