644 



PHYSIOLOGY. 



among others of the sensor-motor region of the 

 cerebral cortex. The activity of the rigid muscles 

 can be readily inhibited by stimulation of various 

 peripheral nerves, among others, of the afferent 

 nerve fibers proceeding from skeletal muscles. Re- 

 flexes obtained from the decerebrate animal exhibit 

 contraction in one muscle group accompanied by 

 relaxation, inhibition in the antagonistic muscle 

 group (reciprocal in nervation)," and this in such 

 distribution and sequence as to couple diagonal 

 limbs in harmonious movements of similar direction. 



From a series of investigations carried on by 

 Elizabeth Cooke in 1894 and 1895 on the. muscles of 

 the frog with a view to determining the part played 

 by osmosis in the animal muscles, and what jdift'er- 

 ences in osmotic phenomena are determined by the 

 different conditions to which living muscles tire 

 subjected, the results are deduced that a muscle 

 immersed in a hypertonic sodium-chloride solution 

 does not behave according to the laws of osmotic 

 pressure governing two solutions having the pres- 

 sure of the immersing lluid and the fluid which is 

 isotonic for the muscle, but (owing doubtless to 

 splitting-up processes within itself consequent upon 

 the taking up of water by the muscle) behaves like a 

 solution having a higher osmotic pressure than the 

 solution for which it is isotonic ; that a rise in 

 temperature determines an increase in the osmotic 

 pressure within the muscle, and this increase is 

 greater than the increase which would result from 

 a given rise of temperature in a solution the mole- 

 cules of which do not dissociate ; that in a muscle 

 which has been removed for some time from the 

 body a loss of water decreases the irritability of the 

 muscle, and a taking up of water, up to a certain 

 point, increases the irritability (beyond that point 

 the taking up of water decreases the irritability of 

 the muscle) ; that a muscle which has done work 

 has a higher osmotic pressure than a resting 

 muscle (the greater the fatigue the greater the in- 

 crease in osmotic pressure) ; and that the increase 

 in the osmotic pressure consequent on fatigue is 

 due not to any change in the physical properties of 

 the muscle, but to chemical changes within the 

 muscle. 



Experiments made upon dogs by J. Brunton 

 Blaikie and Prof. Gottlieb, and reported to the In- 

 ternational Physiological Congress, demonstrated 

 that urea is present in the muscles of both well- 

 fed and starved animals, but that its amount under- 

 goes considerable variation according to the condi- 

 tion of the animal, the variation appearing to be 

 essentially related to the amount of urea in the 

 blood. 



Nervous System. The functions of the optic 

 thalami have been investigated by M. J. Sellier and 

 M. II. \ 7 erger, with special reference to the effect 

 of lesions of them upon sensibility. In experi- 

 ments with dogs fine needles were made to pene- 

 trate the substance of the tSalami and a current of 

 determined mean strength was made to pass. No 

 symptoms of meningitis were observed in any of 

 the animals, and only small, though sharply de- 

 fined, destruction of the tissues was observed. The 

 animals were allowed to recover from the opera- 

 tion and were tested systematically for a few 

 weeks. When they were examined from eight to 

 ten days after the operation, motility and sensi- 

 tiveness to heat were always found intact. The 

 sense of the position of the limbs and the tac- 

 tile sensibility were always manifestly affected. 

 At the end of a fortnight the disturbance of sensi- 

 bility had disappeared, a fact which the authors 

 regard as the most important outcome of their ob- 

 servations. Marked and permanent visual troubles 

 were observed in two cases, but the authors were 

 not able to determine whether there was complete 



unilateral blindness or a crossed hemianopsis. 

 They satisfied themselves that the optic thalami 

 have no influence on the voluntary movements of the 

 animal operated upon, and that there were no com- 

 pulsory or forced movements. Their sensory offico 

 is undeniable, but the thalamie anaesthesia', like 

 cortical ana?sthesia, do not include sensibility to 

 pain and are transitory circumstances which sun- 

 port the view that the functions of the cerebral 

 ganglia are similar to, if not identical with, those of 

 the convolutions of the brain. 



Two tracts in the lumbo-sacral region containing 

 what Marie has named " endogenous fibers " are de- 

 scribed by Dr. Alexander Bruce. These fibers oc- 

 cur in the posterior columns of the cord, and are so 

 named because they are derived from cells in the 

 cord itself and do not originate in the posterior 

 roots. One of the tracts, named thecornu-commis- 

 sural tract, lies in the anterior part of the posterior 

 column in close apposition to the posterior commis- 

 sure and septum and in part to the surface of the 

 cord. The second, the septo-marginal tract, has a 

 close relation to the posterior median septum. The 

 cornu-commissural tract does not degenerate in 

 locomotor ataxia even in its advanced stages or in 

 injury to or compression of the cauda equina. It 

 undergoes degeneration in conditions which lead to 

 atrophy or degeneration of the cells of the posterior 

 cornu. After giving a particular description ( f 

 these tracts, Dr. Bruce observes that it is not yit 

 possible to make a definite statement regarding the 

 cells from which they originate, and that nothing 

 can be asserted with certainty as to their function 

 except that they are probably commissural. 



From studies of the experimental junction of the 

 vagus nerve with the cells of the superior cervical 

 junction Dr. J. N. Langley concludes that there is 

 no essential difference between the efferent " vis- 

 ceral" or "involuntary" nerve fibers, whether they 

 leave the central nervous system by way of the 

 cranial nerves, by way of the sacral nerves, or by way 

 of the spinal nerves to the sympathetic system. All 

 these fibers he takes to be preganglionic fibers, and 

 he thinks that the preganglionic fiber is capable in 

 proper conditions of becoming connected with any 

 nerve cell with which a preganglionic fiber is nor- 

 mally connected, although apparently this connec- 

 tion does not take place with equal readiness in all 

 cases. On the whole it appears that the functions 

 exercised both by preganglionic andbyppst-ganjjli- 

 onic fibers depend less upon physiological differ- 

 ences than upon the connections which they have 

 an opportunity of making during the development 

 of the nervous system and of the other tissues of the 

 body. 



From a study of the changes produced by exci- 

 tations in the cerebral neurones, the results of which 

 were communicated to the International Physiolog- 

 ical Congress, Dr. Heger, of Brussels, concludes thwt 

 one of the important properties of the nervous ce I 

 is its variability. The variations bear upon tin- 

 body of the cell, its prolongations, and its appei.- 

 dixes. The three orders of variations may exi~t 

 together or independently of one another. The in- 

 vestigation of their significance I tears upon the 

 question of the normal and pathological activity of 

 the nervous centers. 



In a paper read to the fourth fnternational Ph\ - 

 iological Congress at Cambridge, England, on tin 1 

 significance of the moniliform stale of the eerebr; 1 

 neurones, M. D. Demoor gave the conclusion thiit 

 the nervous elements being plastic, real amiboi 1 

 movements do not enter into the phenomena. The 

 plasticity of the neurones is very important from 

 the point of view of the mode of their assnciat i< -i 

 with one another, and of their relations with the 

 terminal apparatus. 



ith the 



