532 THE POPULAR SCIENCE MONTHLY. 



vessels and slacken the circulation in almost every case : if they are 

 intense, they even effect its complete check by a strong contraction of 

 the little arterial branches. Continuous currents do not act in this 

 way ; usually they quicken the circulation, while occasioning an en- 

 largement of the vessels, at least, this has been established by Robin 

 and Hiffelsheim, in the microscopic examination of the flow of blood 

 under electric stimulus. Onimus and Legros afterward proved that 

 these movements are governed by the following law : The descending 

 current dilates the vessels, and the ascending current contracts them. 

 A striking experiment proves the value of this law : A part of the 

 skull of a vigorous dog is removed, so as to expose the brain. The 

 positive pole of a pretty strong battery is then placed on the exposed 

 brain, and the negative pole on the neck. The slender and superficial 

 vessels of the brain contract visibly, and the organ itself seems to col- 

 lapse. Arranging the poles in the contrary order, the reverse is re- 

 marked ; the capillary vessels swell and distend, while the substance 

 of the brain protrudes through the opening made in the walls of the 

 skull. This experiment proves the possibility of increasing or lessen- 

 ing at will the intensity of circulation in the brain, as indeed in any 

 other organ, by means of electric currents. Onimus lately made an 

 equally interesting experiment. Many persons know that the famous 

 physiologist Helmholz introduced into medicine the use of a simple 

 and convenient instrument called the ophthalmoscope, by means of 

 which the bottom of the eye may be quite distinctly seen, that is to 

 say, the net formed by the nerve-fibres, and the delicate vessels of the 

 retina. Now, on examining this net, while the head is put under elec- 

 tric influence, the little blood-tubes are plainly seen to dilate and 

 grow of a more lively crimson. 



Let us now study the effect of the electric current on the functions 

 of the motor system, and on sensibility. Aldini, a nephew of Gal- 

 vani, undertook the first investigations of this kind upon human be- 

 ings. Convinced that the proper study of the effects of electricity on 

 the organs required the human body to be taken at the immediate in- 

 stant after the extinction of life, he believed he would do well, as he 

 relates himself, to take his place beside the scaffold, and under the 

 axe of the law, to receive from the executioner's hand the blood- 

 stained bodies which were the only really suitable subjects for his ex- 

 periments. In January and February, 1802, he availed himself of the 

 occasion of the beheading at Boulogne of two criminals, whom the 

 government willingly gave up to his scientific inquiry. Subjected to 

 electric action, these bodies presented so strange a sight as to terrify 

 some of the assistants. The muscles of the face contracted in fright- 

 ful grimaces. All the limbs were seized with violent convulsions. 

 The bodies seemed to feel the first stir of resurrection, and an impulse 

 to spring up. For several hours after decapitation, the vital centres 

 of movement retained the power of answering to the electric excite- 



