158 The Outline of Science 



tigial structures reveal his pedigree. They must have an histori- 

 cal or evolutionary significance. No other interpretation is 



possible. 



Some men, oftener than women, show on the inturned margin 

 of the ear-trumpet or pinna, a little conical projection of great 

 interest. It is a vestige of the tip of the pointed ear of lower 

 mammals, and it is well named Darwin's point. It was he who 

 described it as a "surviving symbol of the stirring times and dan- 

 gerous days of man's animal youth." 



2 

 Physiological Proof of Man's Relationship with a Simian Stock 



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 mon- 

 key, it behaves in a hostile way to the other blood, bringing about 

 a destruction of the red blood corpuscles. But when it is trans- 

 fused into a chimpanzee there is an harmonious mingling of the 

 two. This is a very literal demonstration of man's blood-relation- 

 ship 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 mon- 



