INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 853 



observed in the cells of the higher animals. He finds that the 

 blastoderm cells in Chironomiis send out well-marked pscudopodia 

 (some straight, some bent, others branched) into the space between the 

 egg and its membrane. They are best seen at the upj)er pole of the 

 egg, opposite the polar cells. Their movements are often so rapid as 

 to be with difficulty figured with the camera lucida. Sometimes, too, 

 cells of the blastoderm become detached, and form true wandering- 

 cells, but probably these are subsequently reabsorbed. 



EflFects of Induced Currents on the Nervous System.* — The 

 contribution of M. Schiff on this subject opens up quite a new field of 

 physiological research, which promises to be of extreme importance. 

 He was led to undertake his experiments by having observed the 

 results of M, Charcot's researches on hysteric patients. This eminent 

 physician has demonstrated that on the application of metallic plates 

 to the extremities of hysteric persons, in whom one side of the body 

 appeared more or less completely insensible, sensibility was in a few 

 minutes entirely restored, for a time ; during the operation the oppo- 

 site side was completely insensible, so that it is clear that we have not 

 to do with any general augmentation of the faculties of the organism ; 

 with a magnet similar results can be obtained when it is held at the 

 distance of one or two centimetres from the patient, but in this case 

 the results are more remarkable, inasmuch as it is, of course, possible 

 to affect the patient with the magnet, while he remains totally ignorant 

 of its nearness to him. 



Led by these experiments M. Schiff has lately devoted himself to 

 a series of researches on animals by the aid of an induction coilj 

 the object in view has been to see whether these agents can modify the 

 functions of the nervous system, and if they can, by producing 

 hysterical conditions, reveal to us some method by which these phe- 

 nomena can bo analyzed ; the following are brief indications of some 

 of the results :— 



(1) When the skin of the leg of a frog was touched by the termi- 

 nations of rheophores connected with a very feeble battery the 

 sensibility of the digits to contact was augmented ; this augmentation, 

 which was tested by the reflex movements of a j^ithed frog, was not 

 exhibited until after a latent period of from eight to twenty-five 

 minutes. 



(2) Similar results were obtained with motor nerves. 



(3) The modifications in the functions of the nerves were expressed 

 by modifications in their electrical properties ; thus, if the lower por- 

 tion of the extremity of a frog was submitted for twenty minutes to a 

 feeble induced current, no electric current was to be observed in the 

 sciatic nerve itself. 



(4) When the sciatic nerve was placed between the two poles of a 

 very powerful electro-magnet, the latent period which always inter- 

 venes between the moment of irritating the sciatic plexus and the 

 contraction of the gastrocnemius muscle was slightly increased. 



A series of experiments was also made on dogs, with a view to sec 

 what were the etfects on the nerve-centres of magnetic stimulation. 

 * ' Arch. Sci. Phys. et Nat.,' i. (1879) p. 226. 



