PHYSIOLOGY. 



667 



irregular jagged outline. The protoplasm was 

 largely filled with pigment and fat. The cells 

 of the" foetus contained no pigment. Comparing 

 the foetus with the old man, the volume of nu- 

 cleus was as 100 to G4'2, and the nucleoli observ- 

 able in nuclei were as 53 to 5. It was not found 

 possible to gain much light upon the exact point 

 in question from the brain of the man killed by 

 accident, who was, however, a confirmed alco- 

 holic. In Ihe bees a remarkable difference in 

 size was noticed between young and old brains, 

 the young brains completely filling the brain 

 case, while the old brains were shrunken into a 

 flat cake. The nuclei of the young brains were 

 large and clear, their protoplasm was dense and 

 granular ; while in the old brains protoplasm 

 was almost absent and the nuclei were greatly 

 shriveled in many cases almost beyond recog- 

 nition. The cells were much more numerous in 

 the young than in the old. If we take the nu- 

 cleus to be the source of rejuvenation for the cell 

 protoplasm, the investigation would seem to in- 

 dicate that age is of the nature of final fatigue 

 final, because the source of energy for the nerve 

 cell has dried up at the fountain head. The 

 author does not mean to assert that nerve tissue 

 is of any more importance in relation to physi- 

 ological dying than any other tissue. The exact 

 position held by each must be determined by ex- 

 periments. 



It has long been a matter of dispute among 

 physiologists and neurologists whether the cen- 

 tral region of the cerebral cortex should be con- 

 sidered primarily sensory, sensori-motor, or 

 purely motor. In England it has been con- 

 sidered by many experimenters to be purely mo- 

 tor, and Dr. Ferrier still holds to that view. On 

 the European Continent and in America this 

 view has never found favor; and in England 

 Dr. Bastian has protested against it, and certain 

 eminent neurologists have been led to modify 

 their opinion respecting it. The question has 

 been made the subject of experimental study by 

 F. VV. Mott, who shows in his summary of re- 

 sults that paralysis and defective sensibility in- 

 variably occurred associated together on the op- 

 posite side to that on which lesion of the cortex 

 was made. If the whole leg area was removed, 

 paralysis of the opposite leg took place, perma- 

 nent as regarded the fine movements of the 

 foot, with diminished sensibility to all forms of 

 stimulus for some days after the operation, and 

 a blunting of sensibility that lasted as long as 

 the animals were kept alive. If the more ex- 

 tensive lesion was produced, permanent paraly- 

 sis of the fine movements of the hand and foot 

 and paresis of the other muscles took place ; but 

 even in this case there was a return of coarse 

 associated movements of hip and knee and head 

 and neck, probably due to the action of lower 

 centers. The animals showed for some time 

 after the operation defective sensibility to sen- 

 sory stimuli, and the parts that remained per- 

 manently paralyzed never recovered tactile sen- 

 sibility sufficient to show any response to a clip 

 fixed thereon, whereas the animal would remove 

 a clip from any much less accessible part not 

 thus affected. In fact, in most cases the animal 

 seemed to show a loss of sense of position of the 

 limb. 



The results of Dr. J. S. Risien Russell's ex- 



periments concerning the functions of the cere- 

 bellum lead him to conclude that that organ is 

 one, one lateral half of which does not in any 

 great measure depend for the proper perform- 

 ance of its functions on the co-operation of the 

 other half. The bulk of the impulses pass from 

 one half of the organ to the cerebrum, or spinal 

 cord, without passing to the other half. Three 

 factors are responsible for the defective move- 

 ments which result on ablation of different parts 

 of the organ inco-ordination, rigidity, and mo- 

 tor paresis. The last of these is probably di- 

 rectly due to the withdrawal of the cerebellar 

 influence from the muscles, while the exalted ex- 

 citability of the opposite cortex cerebri, which 

 results after unilateral ablation of the cerebel- 

 lum, is probably a provision for compensation 

 in this and other connections. The alteration 

 in the excitability of the cerebral cortex was the 

 most striking result obtained. There is evidence 

 that the one half of the cerebellum controls the 

 cells of the cortex of the opposite cerebral hemi- 

 sphere, and those of the anterior horns of the 

 spinal cord on the same side chiefly, and on the 

 opposite side to a slight extent. It is further 

 suggested that either the cerebral hemisphere 

 whose excitability is increased inhibits the op- 

 posite hemisphere, or that, under normal con- 

 ditions, one half of the cerebellum inhibits the 

 other half, which inhibition, being no longer 

 operative owing to ablation of half of the organ, 

 allows the other half to exert an increased con- 

 trol on the opposite cortex cerebri, or on the 

 spinal centers of the same side, or possibly in both 

 directions : but which is the most probable ex- 

 planation of the phenomena observed is at pres- 

 ent left an open question. It is urged by the 

 author that instead of looking on the cerebellum 

 as a special organ which has a special function, 

 distinct from those subserved by other parts of 

 the central nervous system, it would be more 

 correct to look on it as a part of that system, 

 having many functions in common with other 

 parts of it, the chief difference, between one part 

 of this great system and another being the de- 

 gree in which different functions are repre- 

 sented in any given part. 



In his " Nouvelles idees sur la Structure du 

 Systerne Nerveux " Dr. Ramon y Cajal presents 

 and extends the doctrine of Golgi, that with 

 very few exceptions "every nerve cell possesses, 

 besides a process of Deiters or cylinder axis pro- 

 longation, also protoplasmic processes, so that 

 each nerve cell appears to be a minute reflex ap- 

 paratus having centripetal or cellulipetal and 

 centrifugal or cellulifugal processes, the former 

 being represented by the protoplasmic processes 

 and the latter by the process of Deiters, both of 

 which possess numerous collateral and terminal 

 fibrils. The transmission of impulses in the gray 

 ceils is effected not by the direct continuity of" 

 the centripetal fibrils" of neighboring cells but 

 by contact or contiguity or apposition of the 

 processes of one cell with those of another. The 

 main function of the cell is of a trophic nature, 

 and the real generation of nerve force will, per- 

 haps, hereafter be proved to take place in the 

 plexus formed by the ramification of the cell 

 processes. 



For his experiments on the relation of sensa- 

 tion areas to movement, Prof. W. 0. Krohn had 



