318 Biology in America 



above tliaii })clo\v and tlicy respond like iron filings in front 

 of an eleetromagnet which has its current suddenly turned 

 on."« 



Our knowledge of what occurs when an impulse is sent over 

 a nerve is very vague, but we have certain knowledge that 

 physical and chemical changes take place in nerve cells and 

 fibers coincident with such impulses, so that we are justified 

 in believing that these impulses are physico-chemical phenom- 

 ena. At the University of Chicago a young Japanese, 

 Tashiro, a few years ago designed a very delicate little in- 

 strument which he calls the biometer, or measurer of life. 

 By means of this instrument he is able to detect traces of 

 carbon dioxide as small as one thirty-millionth of an ounce. 

 If a living nerve fiber be placed in the biometer and stimu- 

 lated by an electrical current it is found to give off carbon 

 dioxide as the other tissues of the body when they are made 

 to work. There is combustion of living matter then when 

 an impulse travels along a nerve. In the body of a nerve 

 cell are certain peculiarly staining masses known as the 

 Nissl bodies. When a nerve cell is stimulated successively 

 several times these bodies disappear. Some chemical sub- 

 stance has been consumed in the activity of the cell. Nervous 

 activity develops electrical currents which can be meas- 

 ured on a galvanometer, and with very delicate instruments 

 electrical currents can even be detected in the resting nerve. 

 The impulse is not instantaneous but requires measurable 

 time for its transmission. The intensity of the impulses 

 can be measured, as one measures the intensity of sound, 

 light, electrical energ>^ or other physical energy. Nerve ac- 

 tion can be checked by means of suitable chemicals (anes- 

 thetics), while on the other hand certain substances, such as 

 sodium, increase it. Anesthetics may produce similar ef- 

 fects in non-nervous tissues and even in non-living matter. 

 Thus Osterhout has shown that small quantities of anesthet- 

 ics in the sea water decrease the electrical conductivity of 

 seaweed, and several obseryers have shown that they check 

 the passage of substances through cell membranes. If char- 

 coal made from blood be mixed with a solution of oxalic acid 

 containing free oxygen, the acid is changed to carbon diox- 

 ide and water, the charcoal acting as a catalyzer. This 

 catalytic power of the charcoal can be retarded by certain 

 substances (i.e., carbon bisulphide) which act as anesthetics 

 and which can also check the action of finely divided plat- 

 inum in the separation (catalysis) of hydrogen peroxide to 

 w^ater and oxygen. If therefore anesthetics produce effects 

 in non-nervous and even in non-living substances similar to 



» Kellogg, V, "Some Insect Keflexes," "Science," XVIII, pp. 693-4. 



