PHYSIOL< )( i V. 



651 



flexor muscle, presenting radial and other heads, 

 which are capable of acting independently, and 

 thereby producing a certain amount of abduction 

 and adduction according to their position with re- 

 gard to the middle line of the hand. Every muscle 

 of the dorsal or abductor series is inserted in com- 

 mon with one of the heads of a short flexor muscle, 

 and in consequence of their close fusion the line of 

 separation between them is somewhat obscured and 

 has been overlooked. The members of the palmar or 

 true adductor stratum have all disappeared from the 

 human hand with the exception of the adductor potli- 

 'iqutis et t, : hence the action has been 



thrown upon certain heads of the short flexors, and 

 in consequence these heads stand out more distinct- 

 ly, especially as their presence is not marked by fu- 

 sion with any other muscle. Wherever true adduc- 

 tor muscles are found, as in certain of the apes, 

 they are inserted in conjunction with those heads 

 of the short flexors which are capable of supple- 

 menting this action. In the case of the human 

 pollex. which possesses the one true adductor mus- 

 cle, not only is this muscle inserted in common with 

 one head (the uluar) of the flexor 'ids. 



but in consequence that head is always obscured, 

 and in many cases extinguished. 



A study of a new method of walking and run- 

 ning called en fle.rion. on account of a sudden bend 

 of the knee at a particular point in the stride, has 

 been made by MM. Comte and Regnault. It is 

 shown that in this method, which has proved to be 

 of great practical advantage in the movement of 

 troops the vertical oscillations of the body are ren- 

 dered more gradual, besides being reduced in mag- 

 nitude. The same point is brought out in a dyna- 

 mographic study of the variations of the pressure 

 on the feet. The sudden variations of pressure dis- 

 appear from the curve. 



The results of an experimental study by M. A. 

 Chauveau of the question as to whether albuminoids 

 take part in the production of external work, seem 

 to show that the amount of nitrogen secreted is 

 practically the same, whether the animal is doing 

 external work or not; they thus confirm the con- 

 clusion drawn by the author from previous experi- 

 ments that the energy necessary for external work 

 is produced by the combination in the muscle of 

 hydrocarbons. 



In experiments on the relation between the ex- 

 penditure of energy in a muscle and the amount of 

 shortening it undergoes. M. A. Chauveau finds that 

 for a given amount of external work done by the 

 muscle, the energy used up is smaller as the muscle 

 is nearer to its maximum length. The determina- 

 tion was made by means of the method of the respir- 

 atory interchai.. 



Nerrons System. The "Lancet" observes in 

 its review of histology in 1896 that the result of the 

 researches of numerous observers has been to sup- 

 port the views of the Spanish microscopist Ramon 

 y f'ajal in regard to the intercommunication of 

 cells and the mode of termination of their 

 showing that in many cases where direct continuity 

 of substance between more or less remote cells was 

 believed to exist an interspace is really present 

 over or through which the nerve impulse must 

 leap in order to be transferred from the axis cylin- 

 der of one cell to the substance of another cell. 

 Abundant evidence has been obtained that the axis 

 cylinder of one cell breaks up into ramifications 

 \vhich partially surround or embrace the cell body 

 with which they are in association. Finding that 

 the neuroglial cells are sometimes small with great- 

 ly ramified processes, and sometimes large with 

 amplified processes. Ramon y Cajal has suggested 

 that there are only two states or forms of the same 

 cells, and has constructed a hypothesis to explain 



sleep. In repose the cells are expanded, 

 or >pn>ad out with numerous ramifying dendrites 

 which interpose themselves between the axis-cylin- 

 der (limitations of one cell and the protoplasmic 

 processes of another, and no nerve current j. 

 In active states of the nervous system, on the other 

 hand, the neuroglial cellules contract, their pro- 

 cesses are withdrawn, and the axis-cylinder pro- 

 cesses and the protoplasmic profiles come in COn- 

 tact, with consequent pa>sai:e of the nerve current. 

 These statements are in the main supported by 

 Kolliker. the second volume of a new edition of 

 whose " Histology " has just been completed. 



The assumption by Longet. which has been gen- 

 erally accepted as a fact, that after division of the 

 facial, hypoglossal, and sciatic nerves (in the 

 the most remote branches of the distal part cc;>- 

 respond to stimuli after the lapse of four days is 

 criticised by Prof. Arloing, who adduces evidence 

 to show that the irritability of the divided n< 

 is not always uniform in the date of departure, and 

 that considerable variations may be observed in 

 different genera and even in different animals of 

 the same species. Ranvier's observations are cited 

 showing differences in the dog, rabbit, guinea pig, 

 and rat. and in young animals and adult, in vigor- 

 ous animals and ailing ones; and Prof. Arloing 

 himself adds his own observations that in the horse, 

 :id mule the persistence of irritability in the 

 branches of the facial nerve after section of the 

 trunk was remarkable, being prolonged in some 

 cases till the thirteenth day. Different nerves seem 

 to vary in their faculty of retaining their irritability, 

 for while in one case the peripheric extremity of the 

 divided facial nerve retained its excitability for 

 five days, the corresponding portion of the divided 

 median and of the moderator of the heart had both 

 lost their excitability between the fourth and fifth 

 day. 



Experiments have been carried on by Dr. Risien 

 Russell to test the explanation offered by Dr. Hins- 

 dale and Dr. Madison Taylor of crossed knee jerk 

 as the result of a centripetal impulse producing 

 activity of one motor area which in turn stimulates 

 the corresponding portion of the other hemisphere 

 and produces a contraction of the adductors of the 

 thigh opposite the one originally struck. In one 

 set of experiments the author divided the corpus 

 caUosum. but even after this, when an active state 

 of the knee jerks was induced by a certain degree 

 of asphyxia, it became possible to elicit the crossed 

 knee jerk. Further, in order to test whether the 

 cerebrum was concerned in the production of the 

 phenomenon, the spinal cord was divided trans- 

 versely in the dorsal region. In the course of a 

 week well-marked exaggeration of the knee jerks 

 ensued, and it was always possible to evoke a crossed 

 knee jerk and even a greatly exaggerated cross jerk. 

 It wa also sometimes observed that a blow on the 

 distal end of the femur or the proximal end of the 

 tibia was followed by contraction of the opposite 

 adductors of the thigh and extensors of the knee, 

 while there was no response in the extensors of the 

 side on which the blow was delivered. The phe- 

 nomenon is not explained, but the fact is merely 

 recorded. Drs. Hinsdale and Taylor regard the 

 phenomenon which has been named re-enforcement 

 as resulting from irradiation of motor impulses 

 from the active centers to other similar centers, so 

 that they and their related muscles acquire a 

 heightened responsiveness to external stimuli. But 

 Dr. Russell points out that any voluntary motor im- 

 pulse directed to the muscles on the contraction of 

 which the knee jerk depends diminishes the possi- 

 bility of eliciting the phenomenon. He mentions 

 that in using the Jendrassik method the extensors 

 of the knee are sometimes brought into action, and 



