658 Sir James Crichion-Broune [May 27, 



Strict analysis will always reveal significant differences between them, 

 but superficially they sometimes closely resemble each other, and if 

 not identical are certainly not antithetical. 



Without troubling you with further comments on it, I may say 

 that Darwin's second principle of Antithesis may, it seems to me, be 

 dispensed with ; and that all the instances of it which he has adduced 

 may be explained by a reference to the principle of Associated Ser- 

 viceable Habits, or of the Action of the Nervous System, or to 

 another principle to which I shall shortly allude. 



Since the time when Darwin wrote on the expression of the 

 emotions, our knowledge of the structure and action of the nervous 

 system, and especially of its crown, the brain, has advanced enor- 

 mously. His book was published in 1872. At that time the 

 experiments performed by Fritsch and Hitzig, in Germany in 1870, 

 were scarcely known in this country, and Ferrier's fruitful and 

 memorable work had not been begun ; and it is since then that the 

 investigations of Munk, Goltz, Schafer, Horsley, Beevor, Tamburini, 

 and others, have unravelled for us some tangled mysteries of cerebral 

 organisation. Thanks to their labours, we now know that there is 

 localisation of function in the brain, or division of labour between 

 the several parts, and that in one of its parts — what we call the 

 motor area — that division is carried out to a considerable degree of 

 subdivision ; so that we have centres presiding over definite groups 

 of muscular movements in the upper and lower extremities — face, 

 neck, and trunk. 



The active part of the brain is the cortex, or mantle of grey 

 matter which forms its surface, covering its convolutions or folds, 

 and enclosing the mass of white or medullary substance within. This 

 white or medullary substance within the cortex or grey matter, and, 

 forming the great bulk of the organ, is made up of communicating 

 fibres which are equivalent to marine electric cables or telegraph 

 wires, and convey currents to and from the brain. They carry to 

 it sensory impressions, or information from the organs of sense, the 

 surface of the body, its interior — indeed from every nook and cranny 

 of it ; they carry from it the mandates of the will to the muscles, 

 and every tissue under its control ; and they carry within it im- 

 pressions putting the different parts of the brain in communication 

 with each other. In the cortex or grey matter are to be found, of 

 course, those communicating fibres that go to or from it, or traverse 

 it ;' but its essential structure consists in brain-cells, its active con- 

 stituents, a diamond-dust of protoplasm arranged in a striatified 

 manner, and of different shapes and sizes — round, stellate, pyramidal. 

 These little cells, scattered amongst the delicate white fibrils, are 

 the true fountains of nerve-energy, into which are gathered the rills 

 of sensory impressions from which flow forth the streams of voluntary 

 and emotional impulses. It is in correspondence with changes in 

 their protoplasm that all mental activities are manifested. These 

 little brain-cells are of different forms, and are diff'erently arranged 



