736 THE POPULAR SCIENCE MONTHLY. 



composed almost wholly of fibers passing transversely between the two 

 sides ; it makes the hemispheres anatomically and physiologically one. 

 Were we to continue our section straight through the middle line of 

 the callosum, we should reach a lateral chamber in each hemisphere. 

 This chamber contains two rather large bodies called the corpus stria- 

 tum and the optic thalamus. The stems or crura cerebri previously 

 mentioned pass into these bodies before spreading out through the 

 hemispheres. The striatum is shaped somewhat like a pear ; it lies in 

 the chamber with its small end forward, and is composed of alternate 

 layers of cell and fiber matter. The thalamus is ovoid, and presents 

 an almost continuous mass of cell-matter traversed by fibers. The re- 

 searches of J. Luys, of which a condensed account may be found in 

 Vol. XXXIX of the " International Scientific Series," are most inter-, 

 esting as respects both anatomy and functions of the thalamus. Luys 

 has discovered four isolated ganglia of cell-matter in the thalamus, 

 situated one behind the other. He has also traced connections be- 

 tween these ganglia and certain organs of special sense. Behind and 

 between the thalami are two smaller bodies called the optic lobes. 

 They consist of two rounded eminences, the anterior ones being 

 called the nates, the posterior the testes. The optic tracts, forming 

 the optic commissure previously mentioned, proceed from the nates, 

 the testes being connected by a band of fiber-matter with the cere- 

 bellum ; commissural fibers join these optic lobes with the thalami. 



I have now named the leading portions of the cerebro-spinal system, 

 and have indicated their general connections with one another. They 

 are nothing more nor less than a series of nerve-ganglia connected 

 among themselves by transverse and longitudinal commissures. This 

 system shows us matter in its most highly organized condition ; fur- 

 ther, this system shows us matter in some positive and necessary rela- 

 tion to consciousness. 



The conclusions which we draw respecting the nature of this rela- 

 tion must, as has been said, be determined by a comparison of the 



Fig. 4.— Portion or the Trttnk op a Nerve, consisting of many emaller cords wrapped up in a 

 common sheath. (Quain, after Sir C. Bell.) A, the nerve ; B, a single cord drawn out from 

 the rest. Magnified several diameters. 



known functions of the system with the distinctive characteristics 

 of consciousness. I come, therefore, now to consider the functions of 

 the cerebro-spinal system in so far as these are known, and in so far as 

 they may be inferred from recent experiments and pathology. 



Functions of the Cerebro-spinal System. — Nerve-matter has, 

 for its general ofiice-work, to bind together the parts of our body. 

 Wherever this matter is divided there is a peculiar division in the or- 



