474 THE TISSUES. 



and corpus callosum. Von Bibra concludes that the amount of 

 phosphorus in brain-fat is very nearly the same in man, other mam- 

 mals, and birds; that its amount is not essentially modified in in- 

 sanity, in old age, in very young persons, and even in the embryo ; 

 and that there is no reason to believe that the intelligence is espe- 

 cially connected with its amount. The fat of the gray matter of 

 the brain, however, contains rather more phosphorus than that of 

 the white matter. 



The other solids, besides fat, alluded to, are albumen, another albu- 

 minoid substance not coagulable by boiling, and the mineral sub- 

 stances usually met with in other organs and in the formative fluids. 

 Sulphates are, however, almost entirely absent, and the chlorine 

 varies much in amount. Of the earthy phosphates, the medulla 

 oblongata contains a larger proportion than other parts of the en- 

 cephalon. They are also more abundant in the brain of amphibians 

 and fishes than in the higher animals. In fact, all the inorganic 

 constituents are least abundant in the brain of man and other mam- 

 mals, greater in birds, and greatest in amphibians and fishes. The 

 ratio of the potash to the soda in the human brain is nearly inter- 

 mediate between the ratios occurring in the ashes of flesh and blood 

 respectively (p. 395). 



Functions of the Nervous System. 



For definite information on this subject, reference must be had 

 to the treatises on physiology. It may here only be remarked that, 

 so far as motion is concerned, the gray matter of the spinal cord is 

 probably the centre of reflex (or diastaltic) motion ; the ganglia of 

 the cerebrum are the centre of the emotional (and sensational) 

 actions; and the cerebral hemispheres are the source of voluntary 

 motion. On the other hand, some part of the cerebrum (and, most 

 probably, the optic thalami) is the centre of sensation; while the 

 sympathetic influences ascribed to the ganglionic nervous system 

 are not peculiar to it, but inhere also in the ganglionic nerve-fibres 

 in the spinal nerves; these fibres also being the probable channel 

 through which emotions affect the organic functions, and especially 

 that of secretion as of the milk, the lachrymal fluid, &c. 



The cerebral hemispheres are also the centre of the intellectual 

 and moral faculties; while the cerebellum presides over the co- 

 ordination of the voluntary motions, but takes no part in the mental 

 phenomena. Certain facts point to the conclusion that it is also the 



