August 29, 1895] 



NATURE 



431 



SCIENTIFIC SERIALS. 



American Journal of Science, August. — The earth a n\agnetic 

 shell, by Frank H. Bigelow. This paper gives the vectors of 

 the polar magnetic field at the earth due to the sun, together 

 with certain deductions from their intensity and distribution. 

 Unless the magnetic permeability of the interior of the earth is 

 less than I, which is highly improbable, the polar vectors 

 obtained must be interpreted as stream lines llowing round an 

 obstacle in the interior of the earth. In other words, the outer 

 stratum of the earth is permeable to the external magnetic forces, 

 while the nucleus is not ; that is to say, the earth is a magnetic 

 shell. The diameter of this impermeable nucleus is calculated 

 at 6340 miles, and the thickness of the shell at 790 miles. The 

 external ]iolar field is concentrated in two belts, one of which is 

 the auroral zone round the poles, and the tropical belt at the two 

 tropics. It is a pity that most magnetic observatories are placed 

 on the middatitude depression. Since both the magnetic and 

 the electromagnetic vectors represent cosmical forces of the same 

 type as gravitation, connecting the sun with the planets, they 

 should be taken into account in general theoretical astronomy, or 

 the celestial mechanics of the solar system. It is possible that 

 certain irregular motions as yet unexplained may be accounted 

 for on the basis of these additional forces. — On the velocity of 

 electric waves, by John Trowbridge and William Duane. The 

 apparatus used for photographing successive sparks whose images 

 were thrown on the plate by a revolving mirror, was substantially 

 the same as previously described ; but the dielectric used was 

 plate glass, and the terminals were made of cadmuim. The 

 average value for the velocity of electric waves travelling along 

 two parallel wires was 3*0024 x 10''* cm. per second, a value 

 w-hich differs from the velocity of light by less than 2 per cent, 

 of its value, and from the ratio between the two systems of 

 electromagnetic units by even less. — On the distribution and the 

 secular variation of terrestrial magnetism, by L. A. Bauer. The 

 distribution and the secular variation appear to be closely related, 

 they obey similar law's, and seem to Ije connected in some way 

 with the rotation of the earth. The following are some of the 

 laws traced by the author ; The mean declination along a 

 parallel of latitude is always westerly, the minimum occurring 

 near the equator. The mean inclination along a parallel of 

 latitude follows quite closely the law ; tan 1 = 2 tan <^ where I is 

 the inclination and ip the geograjihical latitude. The minimum 

 range in declination, and the minimum average secular change 

 from 17S0 to 18S5 along a parallel of latitude occurred near the 

 equator, the values generally increasing ujion leaving the equat<jr. 

 The corresponding values in the case of inclination were maxima, 

 and decrease upon leaving the equator. — Complementary rocks 

 and radial dykes, by L. V. Pirs.son. " Complementary rocks " 

 are such that if the basic types are combined with the accom- 

 panying acid types, they give the composition of the main type 

 of magma with which they are associated. 



SOCIETIES AND ACADEMIES. 



LO.NDON. 



Royal Society, May I. — ^Dr. E. Lindon Melius gave the 

 results of experimental lesions of the cortex cerebri in the 

 Honnet Monkey. The experiments were confined to the left 

 hemisphere, and consisted in the removal of minute portions of 

 the cortex (generally about 16 sq. mm.) representing the centres 

 for movements of the hallux and thumb, as well as several 

 centres within the facial area. The animals recovered from the 

 operation without any sign of .sepsis, and were killed from ten to 

 thirty-five days after the operation, the l)rains and cords 

 hardened in Midler's fluid, and stained by the Marchi method. 

 Numerous as.sociation fibres, both coarse and fine, connecting 

 the lesion with the surrounding cortex, were found tlegenerated. 

 The.se were always most numerous in the immediate neighbour- 

 hood of the lesion, and mostly distributed to the two central 

 convoluti(tns. 



From lesions in the hallux centre degenerated association 

 fibres were distributed to both central convolutions to the level 

 of the inferior genu of the fissure of Rolando, to the parietal 

 lobule, to the posterior portion of the .superior frontal convolu- 

 tion, to the lobulus paracentralis, precuneus, and the gyrus 

 tornicatus. Degenerate fibres crossed in the middle third of the 

 corpus callosum and w'ere distributed to corresponding por- 

 tions of the right cortex, the degeneration on the right side 



NO. 1348, VOL. 52] 



being considerably less than on the left. In the lower levels of 

 the left internal capsule the degeneration was .scattered over the 

 area of the middle third of the posterior limb, being somewhat 

 anterior to its position in higher levels. From the posterior 

 limb of the internal capsule most of the fine degeneration passed 

 into the optic thalamus, while the coarse passetl on into the cms, 

 where it was found in the middle third. \Iany coarse degenerate 

 fibres passed from the crus into the substantia nigra. At the 

 decussation of the j.wramids the tract divides, the larger portion 

 crossing to the opposite lateral column, while the smaller goes to 

 that of the .same side. The amount of degeneration {passing to 

 the lateral column of the same (left) side varies from a third of 

 all the degeneration in one case to about a twentieth in the 

 others. In each case a few degenerate fibres remain in the left 

 anterior column after the completion of the decussation. The 

 amount varies in different cases, and is not apjiarently dejiendent 

 on the proportion ot degenerate fibres passing to the lateral 

 column of the same side. The relations and extent of the de- 

 generated areas remain vmchanged thioughout the cervical and 

 (lorsal cord. The degeneration in the crossed tract of each side 

 is evenly scattered over its entire area, the tw-o sides only differ- 

 ing in the density of the degeneration. In the lumbar region 

 the degeneration in each crossed tract and in the left anterior 

 column begins to go out, and, in the only case examined at that 

 level, the degeneration had not all disappeared at the level of the 

 third sacral root. 



In lesions of the thumb centre (ascending parietal convolution 

 just above the inferior genu of the fissure of Rolando) degenerated 

 association fibres were distributed to the central convolutions 

 from the border of the lofigiludinal fissure nearly to the fissure 

 of Sylvius. To a less degree, but in varying amounts, degenerate 

 fibres were traced to the posterior portions of the middle and 

 inferior frontal convolutions, to the supra marginal and angular 

 gyri, the upper or posterior portion of the superior temporal 

 convolution, the precuneus and lobus quadratus and paracen- 

 tralis and the gyrus fornicatus. Degenerate fibres crossing in 

 the middle third of the corpus callosum were distributed to the 

 corresponding convolutions of the right side, though less in 

 amount and area of distribution. There was a remarkable 

 variation in the size of the fibres distributed to the central con- 

 volutions of both hemispheres, Ijeing coarse above the level of 

 the lesion and fine below', thus corresponding with the measure- 

 ments made by Bevan Lew is of the corpuscles of the fourth layer 

 of the cortex in this region. The arrangement and distribution 

 of the degeneration in the posterior limb of the left internal 

 capsule was the same as in lesions of the hallux centre, and there 

 was the same passage of fine degeneration from the capsule 

 to the thalamus. The amount of coarse degeneration jjassing 

 from the crus to the substantia nigra was much greater than in 

 lesions of the hallux centre, varying from a half to nearly the 

 whole of the degeneration reaching the crus. In one case only 

 was there a division of the degenerated tract at the decussation 

 of the pyramids such as was observed in lesions of the hallux 

 centre, and the amount of degeneration passing to the left 

 lateral colunm was less than in either of the hallux cases. This 

 was also the only case in which .a few degenerate fibres remained 

 in the left anterior column after the completion of the decussation. 

 In two cases s<->me degeneration was foiuid in the right capsule and 

 crus occupying the same position and following the same course 

 as the degenerate fibres in the left capsule and crus, but its 

 direct connection with the lesion could not be demonstrated. 

 From the level of the seventh cervical root downward the de- 

 generate fibres steadily and gradually disappeared, and at the 

 le\el of the third dorsal root there were none left, thus confirm- 

 ing the results obtained by excitation of the nerve roots. 



The lesions within the facial area were, with one exception, 

 along the upper border of the fissure of Sylvius. The single 

 exception was in the a.scending frontal convolution near the 

 inferior genu of the fissure of Rolando. In all these experiments 

 the degenerate association fibres were mostly distributed to the 

 central convolutions, but in .some instances to the posterior por- 

 tions of the middle and inferior frontal, the superior and iirferior 

 temporal convolutions, and the supra marginal gyrus. The de- 

 generation in the corpus callosum was mostly in the anterior 

 half of the middle third, and the distribution of degenerate fibres 

 to the convolutions of the right hemisphere more nearly corre- 

 sponded to that of the left than in lesions of the hallux or thumb 

 centre. In all the lesions of the facial area the degenerations in 

 the uppermost levels of the capsule were in the anterior jiortion, 

 gradually moving backward in ihf Imvir Kvels until thi;y were 



