214 



SCIENCE. 



[N. S. Vol. II. No. 34. 



given out by the cells. As this material 

 for the jelly is poured out the cells gradu- 

 ally shrink to their original size, and then 

 wait another twelve months before doing 

 their destined work. 



If one can thus catch a glimpse of some 

 of the finer processes taking place in gland 

 action, how is it with nervous action, the 

 highest function of which living matter is 

 capable ? While it has been known for a 

 long time that the nervous system is the 

 organ of thought and feeling and the direc- 

 tor and coordinator of the motions of the 

 body, and many speculations have been 

 made concerning the processes through 

 which the nervous tissue passes in perform- 

 ing its functions, it was left to an American 

 student, Dr. Hodge, to first successfully 

 show that there were visible changes 

 through which the nervous system passes 

 in its work. The question is, can the ac- 

 tivity of the nervous system be traced as 

 surely by changes occurring in the living 

 matter forming its basis as the action of a 

 gland can be seen by the study of the gland 

 cells? 



The demonstration is simple now that 

 the method has been shown. N'o doubt 

 every one has had the experience of failing 

 to perform some difficult muscular action 

 at one time and then at another of doing it 

 with ease, or of finding true the reverse of 

 the adage 'practise makes perfect.' For 

 example, in a trial of skill, as in learning to 

 ride a bicycle, all the complicated action 

 may be performed with considerable ease 

 and certainty when one is fresh, but as the 

 practice continues the results become pro- 

 gressively less and less successful, and 

 finally with increasing weariness there is 

 only failure and one must rest. We say 

 the muscles are tired; this is true in part, 

 but of much greater importance is the fa- 

 tigue of the nervous system, as this furnishes 

 the impulses for the action and coordina- 

 tion of the muscles. Now, as muscular 



action can be seen and the amount can be 

 carefully controlled, here was an exact in- 

 dicator of the time and amount of the ner- 

 vous activity. Furthermore, as animals 

 have two similar sides, one arm or leg may 

 work and the other remain at rest, and con- 

 sequently corresponding sides of the nervous 

 system may be active and at rest. By 

 means of electrical irritation one arm of a 

 cat or other animal was caused to move 

 vigorously for a considerable time, the other 

 arm remaining at rest. Then the two sides 

 of the nervous system, that is the pairs of 

 nerves to the arms with their ganglia and a 

 segment of the myel (spinal cord), were re- 

 moved and treated with fixing agents, and 

 carried through all the processes necessary 

 to get thin sections capable of accurate 

 study with the microscope. Finally, upon 

 the same glass slide are parts of the nervous 

 system fatigued even to exhaustion, and 

 corresponding parts of the same animal 

 which has been at rest. Certainly if the 

 nervous substance shows the result or pro- 

 cesses of its action the conditions are here 

 perfect. Fatigued nerve cells are side by 

 side with those in a state of rest. The ap- 

 pearances are clear and unmistakable; the 

 nucleus has markedly decreased in size in 

 the fatigued cells and possesses a jagged ir- 

 regular outline in place of the smooth 

 rounded form of the resting cells. The cell 

 substance is shrunken in size and possesses 

 clear scattered spaces or a large clear space 

 around the nucleus. 



If the nervous substance was not fixed at 

 once, but remained in the living animal for 

 twelve to twenty-four hours in a state of 

 repose, the signs of exhaustion disappeared 

 and the two sides appeared alike . By study- 

 ing preparations made after various periods 

 of repose all the stages of recoverj' from ex- 

 haustion could be followed. 



For possible changes in normal fatigue 

 sparrows, pigeons and swallows and also 

 honey bees were used. For example, if 



