anato:my of vektebrates. 



whence the name Gyrencephala,' proposed for this third sub- 

 class of Mammalia. 



In this subclass, there are no such marks of affinity to the 

 Oviparous Vertebrates as have been instanced in the preceding. 

 The testes are concealed, in adaptation to aquatic life, in Cetacea ; 

 but, in the rest of the subclass, with the exception of the Ele- 

 phant, they pass out of the abdomen, and the Gyrencephalous 



quadrupeds, as a general rule, 

 1-^8 have a scrotum. The vulva 



is externally distinct from the 

 anus. With the exception, 

 again, of the Elephant, the 

 blood from the head and ante- 

 rior limbs is returned to the 

 right auricle by a single pre- 

 caval trunk. The Mamma- 

 lian modification of the Ver- 

 tebrate type attains its high- 

 est physical perfections in 

 the Gyrencephala, as mani- 

 fested by the bulk of some, 

 by the destructive mastery of 

 others, by the address and 

 agility of a third order. And, 

 through the superior psycho- 

 logical faculties — an adaptive 

 intelligence predominating over blind instinct — which are asso- 

 ciated with the higher deve- 

 lopement of the brain, the 

 Gyrencephala supply those 

 species which have ever 

 formed the most cherished 

 companions and ser\itors, 

 and the most valuable sour- 

 ces of wealth and power, to 

 Mankind. 



In Man the brain presents 



an ascensive step in deve- 



lopement, higher and more 



strongly marked than that ])y 



whicli the preceding subclass was distinguished from the one below 



it. Although in the highest Gyrencephala the cerebrum, figs. 148, 



' yvpdw, I wind about; iyn^cpuXos, braiii. lxiv. 



Upper surface of the brain of the Orang-cetaii. 

 (After Sandifort.) 



149 



Vertical section of the brain of tlie Orang-oetan. 

 (After W. Vrulik.) Half uat. size. 



