98 
lungs always occupy but a small portion of the thoracic cavity 
—because they do so when the chest is opened, and their 
elasticity is no longer neutralized by the pressure of the air. 
Chimpanzee. 
Fic. 21.—Drawings of the internal casts of a Man’s and of a Chimpanzee’s 
skull, of the same absolute length, and placed in corresponding positions, 
A, Cerebrum; B. Cerebellum. The former drawing is taken from a cast in the 
Museum of the Royal College of Surgeons, the latter from the photograph of 
the cast of a Chimpanzee’s skull, which illustrates the paper by Mr. Marshall 
‘On the Brain of the Chimpanzee’ in the Natural History Review for July, 1861. 
The sharper definition of the lower edge of the cast of the cerebral chamber in 
the Chimpanzee arises from the circumstance that the tentorium remained in that 
skull and not in the Man’s. The cast more accurately represents the brain in 
Chimpanzee than in the Man; and the great backward projection of the pos- 
terior lobes of the cerebrum of the former, beyond the cerebellum, is conspicuous: 
