NA TURE 



\_Nov. I, 1883 



'hat it was evidently still in an embryonic state, mentioned some 

 examples of the conflicting and contradictory statements made 

 by different authorities as to its electrical resistance. These 

 varied from 13,000 to 2875 ohms and less. Me believed 

 it was enormously overstated, and had for this reason applied 

 himself to make some more accurate determinations. He was 

 at once met by three obstacles :—(i) The difficulty of mahing 

 good contact through the skin of a living man. (2) The limit- 

 ation of the amount of current by pain, and by the fact that the 

 rapid opening and closing of strong circuits produced a tetanic 

 state of muscle. (3) The fact that the human body is an easy 

 electrolyte, almost immediately furnishing currents of polarisation. 



As regards (i), the axiomitic statement seemed to be that the 

 poles must be infinitely large compared with the current they had 

 to conduct. This condition he had attempted to fulfil in five 

 different ways, two at least of which were successful : either by 

 immersing the feet and hands in baths of brine in contact with 

 an electrode of amalgamated lead or zinc of from fifty to a hun- 

 dred square inclies surface, or by soaking these extremities in 

 brine, and then wrapping a strip of flexible lead two feet long 

 by two inches wide about tliem, after the fashion of a surgical 

 spiral bandage. The fact that the skin resistance was thus re- 

 duced to zero was proved to demonstration by an observation 

 already recorded in Nature (September 13, p. 463), from which 

 it appeared that the resistance of a corpse, treated with the sjiiral 

 leaden bandages from foot to foot was I150 ohms, and with 

 solid silver conductors thrust three inches deep into the plantar 

 muscles was actually 50 ohms more. 



Under the heading of contacts it was essential to determine 

 definite anatomical points from which the measurements should 

 start, and which readily admitted of linear verification. Such 

 points existed in the prominence of the ulna at the inner side 

 of the wrist, and the lower edge of the external malleolus at the 

 ankle. The shortest course traversed by the current between 

 these two points had been measured to a quarter of an inch. 



There were three principal directions in which determinations 

 had been made : — 



1 . From hand to hand. 



2. P'rom foot to foot. 



3. From hand to foot. 



No. I was much the same as the height of the subject, and was 

 not liable to great variation. 



No. 2 varied more, since the difl"erence between very tall and 

 shorter men lies chiefly in the legs. 



No. 3 was perhaps the best test of tha average conductivity of 

 the body, since looped currents were sure to traverse the whole 

 trunk, and even caused motor disturbance in the extremities not 

 included in the circuit. 



Three such observations were given, inchidingone on a man of 

 the exceptional height of nearly 8 feet. 



As regards pain, it was noted that the E.M.F. used varied 

 from three to ten bichromate cells of I "8 volts each. Even the 

 first was occasionally complained of, thus incidentally showing 

 the goodness of the contact obtained. In morbid conditions, 

 such as that termed myxojdema, the F,.M.F. of 10 cells or 18 

 volts through a resistance of only 1260 ohms was easily borne, 

 and indeed hardly felt. The third difficulty, that namely of 

 electrolysis, was the most serious : indeed the particular metal of 

 which the electrodes were made sank into insignificance com- 

 pared with the rapid and vigorous polarisation of the moist 

 tissues of the body itself. A rotating commutator on Wheat- 

 stone's plan, and afterwards a metronomic instrument, by w'hich 

 the periods of alternation could be varied, were first used, 

 but with only p.artial success. A more delicate mode of 

 discharging was found in the use of an ordinary com- 

 mutator key worked like a piano with the index and middle 

 fingers of tlie left hand ; a double contact key, putting battery 

 and galvanometer successively in circuit, being beneath the 

 right index finger. The left keys being first depressed alter- 

 nately, the right key produced a double deflection, while the 

 bridge resistance was too low, which was replaced by an oppo- 

 site double deflection when it was intentionally made too high. 

 By watching the galvanometer a point was easil)' found where it 

 ceased to "throw," and then three successive contacts in either 

 direction were taken to determine resi.stance. In spite of all 

 precautions, the second measurement was sometimes a little in 

 excess of the first, owing to a polarisation-current assisting the 

 battery. This, however, never amounted to more than about 

 five ohms, and was easily allowed for. Between each set of 

 observations a short-circuit key, inserted outside the bridge, 



was closed for at least a minute, so as to discharge patient, bath, 

 and electrodes. 



The measurement was then repeated with inverted current, 

 and the mean t.aken. 



One set of examples out of many was read to the meeting. 

 Three men of very different heights were tested according to the 

 following t.able : — 



Height. Weight. Ufna to Foot t) Tool 10 

 malleolus fjot. Iiaiid. 



ft. in. St. lb. ft. in. 



1. Mr. Todd 5 6 ••• 7 13 •■■ 5 9? •■• 945 ••• '3=0 



2. Mr. Shackel 6 3 ... 13 o ... 70 ... 930 ... 1027 



3. Hungarian Giant ... 7 8 ... ... 8 7 ... 930 ... 1032*5 



Two of these were students at St, Thomas's Hospital ; the 



third an Austrian now exhibiting at the Aquarium, and kindly 

 lent to the writer for examination. All the three were singul.arly 

 strong, healthy, well-proportioned men, of active athletic habits. 

 An interesting illustration of physiological laws here incidentally 

 cropped out, showing that, in the normal human body consi- 

 dered as a machine, as is the length of the osseous levers so is 

 the sectional area of the motor muscles. This in the present 

 instance results in an almost complete identity of the electrical 

 resistance, increased length being very fairly balanced by in- 

 creased sectional area in the conductor. A good test of morbid 

 leanness or fatness might probalily be founded on this identity. 



A few words only were given to the variations of human re- 

 sistance in disease and W'ith alteration of temperature. The 

 latter have already appeared in the columns of Nature (on 

 June 14 and September 13). 



As regards the former, six cases of hemiplegia were cited ; 

 three on the right and three on the left side of the body, in all 

 of which the paralysed was found less resistant than the healthy 

 side, in amounts varying from 120 to 730 ohms. The only case 

 which differed from this rule was that of a worker in copper, 

 from whose secretions three milligrammes of metallic copper 

 had been extracted, where the cupreous impregnation obviously 

 modified the general re.-vistance of the body, as the writer had 

 found it to do i a the case of lead and mercury also. 



A confirmation of the view already expressed by the writer of 

 the paper, that the human body follows the law of solid rather 

 than that of fluid conductors under changes of temperature, had 

 occurred in the instance first quoted (June 14, p. 151), where 

 the occurrence of dropsical effusion in the lower extremities 

 permanently reduced the resistance from the values originally 

 given, the lowest of which was 2300, to 750 ohms. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 



Ten lectures on the diseases of field and garden crops Avill be 

 delivered by Mr. Worthington G. Smith, K.L.S., before the 

 Institttte of Agriculture, British Museum, South Kensington, 

 during the week November 12-17. The lectures will be illus- 

 trated with actual examples, and new drawings of all the diseases 

 from nature, unifDrmly enl.arged to looo and 5000 diameters. 



University College, Abervswyth.— Mr. J. Brill, B.A., 

 St. John's College, Cambridge, has been appointed lecturer to 

 assist the Professor of Mathematics at this college. Mr. Brill 

 was fourth wrangler in January I SS2, and, we understand, had 

 the honour of being one of the selected candidates for the Pro- 

 fessorship of Mathematics at the University College, Cardiff. 



SCIENTIFIC SERIALS 



Revue d' Anlhi-opologie (deuxieme et troisieme fascicules), 

 Paris, 1S83. — In the earlier of these two numbers M. Topinard 

 continues the " Elementary Description of the Cerebral Convo- 

 lutions in Man, in accordance with the Schematic Brain 

 designed by Paul Broca." This is the second of the series of 

 explanatory instructions begun in the January number. It ends 

 with a description of the occipital fissures, peculiar to man, the 

 simia:, and lemurs, which Broca termed " scissure oceipitale 

 interne" and "scissure oceipitale e.\terne." In the simite the 

 former of these is generally perpendicular, while in man it is often 

 oblique in direction and irregular in position, rendering its de- 

 termination difficult. — Under the title " Tiansformisme" a term 

 used by French anthropologists for Danvimsiii, M. Mathias 

 Duval gives the substance of his introductory lecture at the 

 Anthropological School at Paris at the opening of the session of 

 1SS1-S2. The lecturer, after giving a general idea of " trans- 

 foraiism," passes in review the services rendered to the modern 

 science of evolution by Daruin's precursors, Lamarck and 

 Etienne Geoffroy Saint-Hilaire. Next he considers the re- 



