Comparative Anatomy of the Brain. 601 



The weight of the whole brain in adult man runs from 40 to 60 oz. 

 In woman, from 36 to 50. The maximum of a healthy brain is about 

 64 oz. , the minimum, 31 oz. Idiots sometimes run as low as 16 oz. 

 In a brain weighing 51 oz. , about the average of an adult male, the 

 weights of the subdivisions would be about as follows : Cerebrum, 42|- 

 oz. ; cerebellum, 5^ oz. ; medulla oblongata, optic thalami and corpora 

 striata, altogether, 3 oz. The spinal cord would weigh about If oz. 

 The brain equals about one thirty-seventh of the whole man. ( Carpenter. ) 



FIGS. 343, 344, 345. View of in 

 (mesial) surface of hemisphere 

 bit (top fig.); Pig (middle ); C? 

 zee ( bottom fig.). 



Ol. Olfactory lobe. 



cc. Corpus callosum. 



Ac. Anterior commissure 



H. Hippocampal sulcus. 



Un. Uncinate gyrus. 



M. Marginal 



G. Callosal 



Ip. Internal perpendicular. 



Ca. Calcarine sulcus. 



Coll Collateral " 



F. Fornix 



Lt. Lamina terminalis. ( Huxley.) 



The average weight of 

 Horse's brain is 22.9 oz., and 

 of the spinal cord 10. 1 oz. The 

 brain of the Ass weighs 12.7 

 oz. , and the spinal cord 5. 3 oz. ; 

 that of the Ox 16.9 oz., the 

 spinal cord 7.8 oz. ; that of the 

 Sheep and Gloat 4.6, and the 

 spinal cord 1.8. The brain of 

 the Pig weighs 5. 6 oz. , the spi- 

 nal cord 2. 4 ; that of the Dog 

 6.3^ the spinal cord 1.2; that 

 of the Cat 1.1 oz. , and of the 

 spinal cord 0.3 oz. The brain 

 of the Chicken weighs 0.16 of 

 an ounce, that of a large whale 

 80 oz. , that of an elephant, 160 oz. 



Nerves. In the Ornithorhynchus the olfactory nerve leaves the olfac- 

 tory lobe on each side in a single bundle, and without dividing passes 

 entire through the skull, as in Birds and Lizzards. In all the other 

 mammals the trunk is subdivided into a greater or less number of nerves, 

 each one passing through the skull by an orifice of its own. In the 

 Echidna and the marsupials the number of nerves and the holes in the 

 cribriform plate through which they pass is very great. The surface of 

 pituitary membrane is also of great extent. In all the families between 

 the Ornithorhynchus and the quadrumana, the number of the olfactory 



FlGS. 343. 344, 345. 



