308 NERVE-TISSUE. 



earlier period of existence." This is on an average, for some tissues contain 

 much less living matter; the bones, for example, only one-twentieth, and 

 some textures, when old, not more than one-hundredth.' 



" I have made this long quotation from Drysdale's book, because I am 

 anxious to do full justice to Beale, and I could not find a statement of his 

 views so succinct for quotation in his own writing. The objection, however, 

 urged by Bastian to Beale is so very pertinent that it must also find a place 

 here, but I shall not dwell upon other points on which Beale differs from the 

 bioplasson doctrine ; such as that living matter exhibits the same characters 

 at every period of its existence, and that it is always perfectly structureless. 

 ' It has always appeared to me/ says Bastian,* l to be a very fundamental 

 objection to his theory, that so many of the most characteristically vital 

 phenomena of the higher animals should take place through the agency of 

 tissues muscle and nerve, for instance by far the greater part of the bulk 

 of which would, in accordance with Dr. Beale's view, have to be considered 

 as dead and inert.'" 



Meynert's view that the cortex of the brain is a mirror, on which, by means 

 of the conducting nerves, impressions from the outer world are projected has 

 in late years decidedly gained ground. He found that the nerves of the 

 special senses go to special convolutions of the cortex of the brain, and that 

 from other convolutions arise nerves which control muscle action. Hitzig 

 was the first who discovered points in the cortex of the brain of the cat, 

 which, upon being stimulated by electricity, produced regularly recurring 

 motions in the extremities. Later, Terrier and Munk demonstrated in the 

 brain of apes the isolation of special sensory perception and of muscular move- 

 ments, usually subject to the will. Their experiments confirm the anatomical 

 premise of Meynert in its general bearings. It was found that, by cutting 

 away a certain part of the brain of these animals, blindness would result, 

 while the removal of another part was followed by deafness, and of still 

 another by paralysis. If the latter parts, instead of being removed, were 

 stimulated by electricity, special motions followed, as if they were produced 

 by the will of the animal. These observers found the keys of the mind of the 

 animal in the gray substance of the convolutions of the brain, and, by touching 

 a special key, could simulate the expression of the animal's feelings. 



Pathological processes in the brain have greatly aided in corroborating the 

 localized nature of sensory and motor functions. Meynert especially pointed 

 out the center of speech by the study of aphasia, which is a loss of the power to 

 pronounce certain words. This center is in the Eeil's island, with the claustrum 

 outside the third member of the lenticular nucleus. Meynert pointed out, in a 

 series of careful researches, that the claustrum is a component part of the cortex 

 of the island, the cortex around the fossa Sylvii, and the posterior orbital con- 

 volution. It represents the fifth layer of the cortical structure, which is more 

 than usually developed and serves for a broad connection with other territories 

 of the cerebral cortex. The connection of the claustrum with an auditory 

 bundle renders the walls of the fossa Sylvii a field for sound, while the connec- 

 tion of the claustrum with the fibrous systems of the medulla of the island of 

 Beil and the external capsule of the lenticular nucleus renders this field of 

 sound a central organ of speech. Aphasia depends on a destruction or a 



* "The Beginnings ol Life: being some account of the Nature, Modes of Origin, and 

 Transformations of Lower Organisms." London, 1872, vol. i., p. 155. 



