Page:Mind (Old Series) Volume 9.djvu/107

 BILATERAL ASYMMETRY OF FUNCTION. 95 but simultaneously reduced or lost on the corresponding point of the sound side. Analogous restorations were observed by the Burq-Charcot commission of the French Biological Society in 1878, in the field of each of the other senses, on the application of metals. The phenomena of transfer, designated by Adam- kiewicz a " bilateral function," like sweat-secretion, though quite often complicated with simulation and lasting sometimes for many hours, is, in a sense, the reverse of the familiar increase of discriminative sensibility on the corresponding part of the other half of the body during psycho-physical observations. The most familiar asymmetry in both form and function is in the hands and arms. One man in from about twenty to forty, according to various enumerations, is left-handed. Ogle found that fifty-seven men and twenty-eight women in one thousand were left-handed, and cases of true ambidexterity are very rare, as tools, machines, and many occupations and specialisations of man, unlike those of woman, often make it practically impossible. The difference is very manifest in the shoulders and chest, while the right arm is often nearly a third of an inch longer, displaces several cubic inches more of water when immersed in a tube up to a given point, as we have observed, and is sometimes one-third stronger, so that the deflections of the needle caused by muscular effort is greater on this side. The weight of the arms is so important in correcting the oscillations of the centre of gravity in walking that, if one be lost, a runner needs another of the same weight. This inequality alone brings this centre somewhat to the i-ight. The two hands at rest are unequally open, and pronated or supinated, and an ingenious acquaintance is quite successful in inferring, at an evening party, a stranger's occu- pation by the way in which the hands and arms are carried and moved. Even the papillary striation, often almost as characteristic of an individual as his photograph is of his features, is different on the corresponding finger-tip of the two hands. The legs also, despite their similar action in walking, their most common act, present differences, like though less, as is seen in the unequal wear of shoes, &c. In one series of measurements, the right leg was found from one to seven-eighths of an inch the longer, and the right tibia has been found to con- tain more calcareous salts and less inorganic matter. The careful weighing of the muscles of the legs and of the back, excised from the body, showed the right to be in excess. Many have a decided preference for the right leg in jumping, kicking, wrest- ling, &c. ; and it has been said that, from a square standing posi- tion, it is most natural to step off right leg first. Few sit cross- legged either way equally well, or turn out the toes equally. Few also can walk on even ground or swim straight, as the mole bur- rows, with their eyes closed. The power of orientation is soon lost ; we wander and then take a fresh start, only to deviate again in the same direction. We are now making further studies here.