PHYSIOLOGY. 



755 



was an interesting fact that, after the injury 

 of the cerebral cortex, the degeneration of the 

 three centers of optic nerves was of a different 

 character from that which set in after the 

 peripheric emicleation. The corpus genicula- 

 tum and the pulvinar were now altered in 

 such a manner that it was mainly the cells 

 which either showed degeneration or were 

 entirely wanting. In the anterior corpora 

 quadrigemina, likewise, it was other layers 

 namely, the third medullary layer and the 

 larger cells which were overtaken by de- 

 generation. The author had had the oppor- 

 tunity, in making a dissection, of substantiat- 

 ing on a man, who had long been suffering 

 from a diseased retina, that the degeneration 

 in the case of man propagated itself centrally 

 toward the three centers before mentioned 

 just as much as in the case of the rabbits 

 operated on. 



Ph. Rey has communicated the following 

 from materials left by him, as the results of 

 347 observations collected by Broca on the 

 weight of the three cerebral regions, frontal 

 lobes, occipital lobes, and parietal regions: 

 First, the relation of these different parts to 

 the brain is, in men : Frontal lobes, 1 : 2*33 ; 

 occipital lobes, 1 : 10*66 ; parieto-temporal re- 

 gions, 1 : 2-12. In women : Frontal lobes, 

 1 : 2-32 ; occipital lobes, 1 : 9-88 ; parieto-tem- 

 poral regions, 1:2'13. Secondly, in man the 

 left frontal lobe is heavier than the right, 

 but in the occipital lobes and in the temporal 

 regions the excess is on the right side. Third- 

 ly, in old people loss of weight is more per- 

 ceptible in the parieto-temporal regions than 

 in the frontal and occipital lobes ; that is par- 

 ticularly the case in women. Hence it is that 

 if in adult life men have proportionately larger 

 frontal lobes, that ratio is attained in women 

 in old age. Fourthly, in men the frontal lobes 

 attain their greatest weight at thirty-five years, 

 but the parieto-temporal regions acquire it at 

 twenty -five. The anterior lobes of women 

 present little difference between twenty -five 

 and thirty -five years. 



"W. H. Gaskell shows, from experiments on 

 the dog, that the nerves which supply the mus- 

 cles of the ?ascular and visceral systems all 

 have certain common histological character- 

 istics, while nerves of the same function pos- 

 sess in addition a well-defined anatomical 

 course. They are all composed of medullated 

 fibers of the finest size, which lose their me- 

 dulla and become non-medullated before they 

 reach their destination. One of the functions 

 of the ganglia with which they are in connec- 

 tion is to effect this conversion of mednllated 

 into non-medullated fibers. A beginning has 

 been made in defining the anatomical course 

 of these nerves by tracing for each kind of 

 nerve the characteristic small medullated fibers 

 from the central nervous system into the spe- 

 cial group of ganglia in which the loss of the 

 medulla takes place. Although this anatomical 

 course can not at present be defined in every 



case to its fullest extent, sufficient evidence 

 has been given to warrant the conclusion that 

 the vascular and visceral muscles are through- 

 out supplied by two kinds of nerve-fibers of 

 opposite functions, the one motor and the 

 other inhibitory ; and that these two kinds of 

 nerve-fibers reach the muscle by separate dis- 

 tinct anatomical paths, the difference of path 

 consisting in a difference of origin from the 

 central nervous system combined with the fact 

 that inhibitory nerves lose their medulla in 

 more distinct ganglia than the corresponding 

 motor nerves. In addition, the ganglia are 

 shown to possess a nutritive power over the 

 nerves which pass from them to the periphery. 

 A third function of the ganglia to "be noticed 

 is the increase in the number of nerve-fibers 

 which occurs simultaneously with the loss of 

 the medulla. The fact that involuntary mus- 

 cles are supplied with two efferent nerves, 

 which differ not only in function but also in 

 their anatomical course, leads to the concep- 

 tion that a similar double nerve exists for all 

 tissues. The sphincter muscle of the iris also 

 affords an example of a muscular structure 

 supplied by two nerve? of opposite character, 

 the one motor and the other inhibitory. The 

 experiments show that the inhibitory nerves 

 are of as fundamental importance in the econ- 

 omy of the body as the motor nerves. No evi- 

 dence exists that the same nerve-fiber is some- 

 times capable of acting as a motor nerve, some- 

 times as a nerve of inhibition, but on the con- 

 trary the latter nerves form a separate and 

 complete nervous system subject to as definite 

 anatomical and histological laws as the for- 

 mer ; the complete investigation of these laws 

 is one of the most important problems of phys- 

 iology, and is absolutely necessary before we 

 can attempt to understand the part played by 

 the nervous system in the regulation of the 

 different vital processes. 



H. P. Bowditch and J. W. Warren, regard- 

 ing the methods of investigation of the vaso- 

 motor nerves of the limbs by observations of 

 the temperature of the skin as not likely to 

 yield wholly satisfactory results, devised and 

 applied a method in which the vascular changes 

 are directly registered by means of a plethys- 

 mograph. The leg of the animal was, in this 

 apparatus, placed in a leg-holder, in which its 

 dilatations and contractions were exactly meas- 

 ured. Under electrical stimulation changes oc- 

 curred in the size of the leg in nearly all cases of 

 one of three sorts: 1. A prompt contraction; 

 2. A prompt contraction, followed by a dilata- 

 tion ; 3. A slow dilatation. Occasionally a dila- 

 tation, followed by a contraction, was observed, 

 but these cases were so irregular in their ap- 

 pearance and so few in comparison with the to- 

 tal number of observations that they were left 

 out of account in the analysis of the results. 

 The results of 990 observations on 70 cats 

 showed that stimulations of every rate and 

 intensity may give any one of the three re- 

 sults, except that simple dilatations were never 



