174 Wortman — Studies of Eocene Mammalia in the 



over, so that he may inspect it more closely, and the raccoon 

 and hear do this more frequently, but the lack of opposability 

 of the thumb places great difficulties in the way of handling 

 an object to any considerable extent. 



Among the monkeys, on the other hand, information of a 

 strange or suspicious object is obtained by sight, at first 

 always at a respectful distance. If the animal is assured that 

 no imminent danger threatens, he will cautiously approach for 

 closer scrutiny; if harmless, he soon takes the object in his 

 hands and inspects it carefully upon all sides. If there is any 

 internal mechanism to excite curiosity, it is forthwith pnlled in 

 pieces or broken, in order that every part may be examined 

 attentively. It is only in case of an article of food that he 

 uses his sense of smell. In this extensive use of the hands, the 

 monkey exhibits traits and capabilities for the acquisition of 

 knowledge far in advance of all other mammals. Not only is 

 there great curiosity, but an active desire for information of 

 all things new or strange in his surroundings. The undisputed 

 testimony of many excellent observers could be quoted in sup- 

 port of this assertion, but the facts are so well known that it is 

 scarcely necessary. 



That which interests us most in this connection is the extent 

 to which the animal makes use of the prehensile extremities in 

 acquiring information and satisfying curiosity. There can be 

 little doubt that, as in man, the sense of sight is the source 

 from which the greatest amount of information is derived ; but 

 at the same time the ability to pick up, handle, and closely 

 inspect any object, — possible only with prehensile extremi- 

 ties, — has constituted a most powerful aid in acquiring knowl- 

 edge of the smaller details. The constant action and reaction 

 of this process, with its inherited effects, upon the brain, 

 throughout innumerable generations, we may readily believe, 

 have resulted in an ever widening circle of psychic activity and 

 cerebral development. 



Another factor which may have had its share in the process 

 is the particular way in which the brain has received its sup- 

 ply of blood from the heart. As we have already seen, the 

 arrangement of the entocarotid circulation is different in mon- 

 keys, apes, and man, from that found in the lemurs. In one 

 group of the lemurs, the blood through the entocarotid is car- 

 ried directly to the base of the skull, where the artery enters 

 the middle or cerebral chamber. In another group, the blood 

 is delivered into the posterior chamber of the skull through a 

 foramen alongside the otic bulla, or ear pouch. In monkeys 

 and man, the entocarotid pierces the petro-tympanic, and 

 delivers the blood directly to the base of the brain in the mid- 

 dle chamber. As far as directness of supply is concerned, the 



