OMNIVOROUS MAMMALS 225 



primitive creatures technically known as Protochordates. First, 

 then, as to Mammals. 



MAN AND MONKEYS (PRIMATES) 



The majority of the forms belonging to this order (including 

 Man and Monkeys) are omnivorous, though some monkeys are 

 pure vegetarians, and the lowest included species, i.e. the Mar- 

 mozets of South America, feed chiefly on insects and other small 

 creatures. A preliminary account of the structure of the human 

 body has already been given (vol. i, pp. 24-59), but a few points 

 related to the feeding-habits may usefully be reviewed here. The 

 teeth, for example, differ on the one hand from the specialized 

 carnivorous condition seen in, say, a cat, and on the other hand 

 from the marked adaptation to a vegetable diet found in a sheep 

 or ox. In a cat we find small pointed incisors, large tusk-like 

 canines, and sharp-edged cutting cheek-teeth. In an ox, on the 

 contrary, there are cutting lower incisors and canines biting 

 against a hard pad above (upper teeth to correspond being 

 absent), and elaborately folded cheek-teeth adapted for grinding. 

 In Man the incisors are chisel-like, the canines pointed but not 

 aggressively large as in the Cat, and the cheek-teeth, with grinding 

 crowns, much less complex than in the sheep. The salivary 

 glands of the human species, organs of which the secretion is 

 specially suited for acting chemically on starchy food, are tolerably 

 well developed, but very much smaller relatively than in the purely 

 vegetarian Ox. Taking the other parts of the digestive organs 

 in the three contrasted forms, we find a short gut, simple stomach, 

 and small caecum in the Cat; long gut, complex stomach, and 

 large caecum in the Ox. The meaning of these differences is that 

 fleshy food is comparatively easy to digest and absorb, vegetable 

 food relatively difficult, hence the shortness and simplicity in the 

 one form and the length and complexity in the other. The gut of 

 Man is of moderate length, the stomach simple, and the cacum very 

 small. It may further be added that human beings thrive best on 

 a mixed diet, as has been shown by numerous experiments. 



LEMURS (LEMUROIDEA) 



The curious LEMURS that have their head-quarters in Mada- 

 gascar, but which are also represented in continental Africa and 



VOL. II. 47 



