172 THE AMEEICAN MONTHLY [August, 



to the electro-motive force divided by the resistance. From this it is 

 seen that the stj'ength of the current passing througli an electrolyte, be 

 it a portion of the human body or a decomposable liquid as in electro- 

 plating, is measured in amperes, or fractions of an ampere ; the force of 

 the currents in volts, and the resistance of the electrolyte to the passage 

 of the current in ohms. In medical application of electricity the 

 current strength is measured in yu-Vtt of an ampere or milliamperes, 

 the sensory nervous system being incapable of withstanding strong 

 currents. The milliampere-meter is considered an essential feature of 

 the electro-therapeutical armamentarium, as with it the effects of weak 

 or strong currents may be observed and systematically noted. 



Density of the current indicates the relation of the strength of the cur- 

 rent to the transverse section of the conductor which it traverses. This 

 might be exemplified by allowing a contact with the top of the head 

 and lower portion of the body of an animal ; the density in the neck 

 would be much greater than either in the head or body, owing to the 

 less area of cross-section of the former. 



THE INFLUENCE OF ELECTRICITY UPON THE LOWER FORMS OF LIFE. 



Slight electric shocks from a coil (induced current) increase the ra- 

 pidity of the protoplasmic movements ; stronger ones cause tetanic con- 

 traction ; and numerous and powerful ones produce coagulation. "A 

 constant current causes contraction and imperfect tetanus; and if pow- 

 erful and long kept up, the positive pole 2Droduces in tlie amoebae near 

 it the same changes as dilute hydrochloric acid, and the negative pole 

 the same changes as are produced by an alkali, such as potash." Upon 

 infusoria, weak electrical currents first quicken the ciliary motion and 

 cause movements of rotation, then swelling of the protoplasm, slower 

 movements, and, finally, apparent solution of the protoplasm. Mod- 

 erate currents produce a tetanic contraction of the protoplasm, and of 

 the cilia, while the contractile vesicle is unaftected. Strong currents 

 cause liquefaction of the protoplasm. (Pharmacology, Therapeutics, 

 and Materia Medica, by Laudr. Brunton, 1SS5.) 



Dr. Klein, in the " Handbook for the Physiological Laboratory," 

 gives an interesting account of the action of electricity on blood. He 

 explains the method of placing the blood on a slide provided with two 

 poles, when the cover-glass being placed on the slide, the examination 

 is made. According to Rollet, it is advisable in using electrical dis- 

 charges, that the tin foil poles should be six millimeters apart. The 

 Leyden jar should have a surface of 500 square centimeters, and give a 

 spark one millimeter long. If, then, the discharges succeed each other at 

 intervals of from three to five minutes, the following changes are observed 

 in the colored corpuscles of man : First, the circular discs become 

 slightly crenate. This effect gradually increases, the corpuscles become 

 rosette shaped, then mulberry shaped, and, finally, by the accumina- 

 tion of the projections, horse-chestnut shaped. Later, the processes 

 are withdrawn, the blood corpuscles become round, and at last, pale. 

 The effect on the white blood corpuscles during their movements is to 

 cause them to assume the spheroidal form, but they resume their move- 

 ment as soon as the current, if not too strong, is discontinued ; under 

 the influence of successive shocks of greater intensity, they swell out, 

 their granules exhibiting molecular movement, and finally disappear. 



