152 



NA TURE 



\June 14, 1883 



perature (7 F.) afforded the opportunity I had long been 

 seeking. But it was some time before I could arrange 

 suitable apparatus for its examination. A hospital ward 

 is an awkward place for Wheatstone's bridge and delicate 

 galvanometers. Moreover I had before found that from 

 the peculiar condition* of the human body, the testing 

 current, to produce accurate results, requires to be fre- 

 quently reversed, for fear of opposition currents of polari- 

 sation. I am glad to see a confirmation of this observa- 

 tion in a verbal communication of Prof. Rosenthal to the 

 Physiological Society of Berlin on April 13. 



It was partly to overcome this difficulty that I devised, 

 at Mr. Preece's suggestion, a dynamometer for alter- 

 nating currents, of which the general arrangement was 

 described in Nature some time ago. It was also 

 brought before the Physical Society at their June meeting 

 in Oxford. Although severely criticised by some mem- 

 bers of that learned body, it works extremely well, and 

 may be, I hope, an addition to medico-electrical ap- 

 pliances. For the purpose of the present experiment I 

 found that an ordinarily sensitive galvanometer, con- 

 siderably damped by air-resistance, was sufficient, since 

 by the zero methods of balancing, it is only necessary just 

 to see the deflection before commutating; when balance 

 is obtained, commutation has no effect on the needle of 

 the bridge. 



It would require more space than could probably be 

 here afforded to give all details of the experiments, 

 which, moreover, by the courtesy of Capt. Douglas 

 Galton, I hope to bring before the British Association of 

 this autumn. But a brief summary of results is as 

 follows : — 



On June 5 I reached the ward at 9.40 a.m. The rigor 

 had begun at S.30 and was beginning to decline ; I had 

 time, however, for the following determinations : — 

 940... ... ... ... ... R. 4140 ohms. 



9-SS .. 347° .. 



10.10 .. ,, 2900 ,, 



These measurements were taken with a very small 

 E.M.F. of about 9 volts. On June 9 I succeeded in 

 reaching the ward during the beginning of the rigor, and 

 took the following measurements, this time with cor- 

 responding temperatures : — 



10.30 a. m Temp. 102° 4 ... R. 4550 



IO.4O ;, ,, I04' 2 ... ,, 463O 



10.50 ,, „ lD4°-2 4930 



At this point the rigor, temperature, and resistance began 

 to descend. I visited the patient again at 



215p.n1 Temp. 103" ... R. 2300 



The apparatus in these observations was left un- 

 touched, so as to prevent any accidental change. The 

 measurement was made with a double E.M.F. to those 

 preceding, namely, 18 volts. I determined on each occa- 

 sion the resistance of the leads and terminals, which I 

 found to be on each occasion 2 ohms. 



I cannot help thinking that the difference, which is as 

 nearly as possible twice the smaller amount, is too great 

 to be accounted for by any instrumental error, and that 

 the human body, in spite of its large amount of liquid 

 constituents, follows a similar thermal law of resistance 

 to that influencing solid conductors, though in a very 

 much higher ratio. 



Only one other point requires comment, namely, the 

 mode of making contact between the body and the testing 

 apparatus. Prof. Rosenthal in the communication quoted 

 above draws attention to the high insulating powers of 

 the epidermis. In the above experiment I passed the 

 current through the two legs, from one foot to the other, 

 in alternate direc'ions. The feet were previously soaked 

 in salt and water ; two large pans containing about a 

 quart of brine each were then placed under the feet, and 

 in each was immersed a plate of copper five inches square 

 connected with the bridge by stout cables. I have found 

 in other experiments that after half an hour the resistance 



ceases to decrease, a.id in this experiment it actually in- 

 creased to the amount of 480 ohms. The whole foot was 

 immersed, its sole resting directly on the copper plate. 

 I have two other methods of making contact in use. The 

 first consists of rubbing the skin with the oleate of mer- 

 cury ; which to the diffusion power of oleic acid adds the 

 conductivity of its base, and then immersing the part in 

 metallic mercury. The other consists of inserting small 

 silver claw-forceps, known to surgeons as "serrefines," 

 through the epidermis into the tissue below. This is 

 rather painful, but not more so than I find medical stu- 

 dents eager in the pursuit of knowledge can and will 

 easily undergo. W. H. Stone 



THE AMBER FLORA ' 



T^HIS is the first volume of a work on the flora of the 

 1 amber-bearing formations of East Prussia, and is 

 devoted exclusively to Coniferas. The introduction con- 

 tains a sketch of the geological history of the order, and 

 among much that is of interest we find an estimate that 

 the existing Conifera; occupy an area of about 3,000,000 

 square miles (500,000 German). The described fossil 

 species are now almost as numerous as the living (400 to 

 450), though a revision might reduce their number by 

 one-half. The colossal dimensions of some of the living 

 Conifers; are familiar to most, but it is not generally 

 known how nearly these are rivalled by fossil species- 

 Examples are given, as of a stem of Cupressinoxylon 

 ponderosum, broken at both ends and 200 feet long, and 

 another 12 to 14 feet across ; a stem of Araucarites, 25 

 feet in circumference, and a silicified stem from Califor- 

 nia, 33 feet round the butt. 



A considerable portion of the work is occupied with a 

 minute and splendidly illustrated inquiry into and descrip- 

 tion of the microscopic structure of the tissue of existing 

 and fossil Conifera;, especially with regard to their resin- 

 secreting organs. Goeppert claims to have originated 

 this study forty years ago, and is certainly the chief au- 

 thority in it. The result of his work shows that the 

 Abietinea;, or fir tribe, have almost alone contributed the 

 amber, and that at least six species produced it, the chief 

 being close allies of the Common Spruce and the Ameri- 

 can Finns strobus. These possess three separate sets of 

 resin-producing organs chiefly situated in the cambium 

 layers, which are in the form of cells and ducts running 

 in both horizontal and vertical directions, and appearing 

 at a very early stage of growth. Some Pines are liable 

 to frost-cracks, and into these the resin collects and 

 thence exudes, keeping the wound from healing and fur- 

 nishing a perpetual supply. Very few specimens of 

 amber wood preserve the bark layers with the resiniferous 

 organs, but sufficient is seen to prove that these in no 

 way differed from those of the Abietineae at the present 

 day, especially of the Spruce. 



The most important section of the work probably is the 

 research into the microscopic structure of the wood,,whicb 

 is, however, of an extremely technical nature. Five sepa- 

 rate species of Finns are recognised by their wood, and a 

 very rare and doubtful wood-structure is referred to the 

 Taxineae. 



More interesting perhaps to the general reader are the 

 descriptions of fragments of foliage and fructification 

 inclosed in the amber. Insignificant as the figured speci- 

 mens appear, they are yet in so marvellous a state of 

 preservation that their texture and microscopic structure, 

 and even the glaucous colouring of the under sides of some 

 of the leaves are visible. Twenty species are determined, 

 with a tendency, it is pleasing to find, rather to curtail 

 than to multiply the number previously des:ribed. They 

 have been studied with extraordinary care, and the results 

 are consequently unusually satisfactory. 



* "Die Flora des Bernsteins." R. Goeppert and A. Menge, Naturfors- 

 henden Gesellschaft in Danzig. 4to, 1883. 



