Show THE MECHANISM OF TOUCH Phenomena of Nerve Telegraphy CurIous Experiments BY EUGENE MURRAY AARON PH DAs D-As the reader holds this paper in his hand there are two ways by which he is made aware of its presence therein One of these is sight the other is the < sense of touch or tactile sensibility as the scientists call it Touch is probably tho least complex com-plex of the five senses Yet examination examina-tion shows it to be far from a simple system by which the tactile sensibility of the finger tips is conveyed to that portion of the brain with which the reader knows that the paper in his hand Throughout the surface of the skin and mucous membranes there are numberless num-berless papillae highly sensitive points rising above the surface These are I outposts of the sense of touch They may be plainly seen under a powerful power-ful lense and are best observed on the tip of the tongue In many of these papillae are minute bulbous organs known as tactile corpuscles or terminal ter-minal bulbs The bulbs themselves I are again divided into several portions These bulbs are the telegraph keys whereby messages are sent from all parts of the body to the main office of the brain Nor does this analogy with telegraphy end here for just as the electrician will tell you that the electric elec-tric fluid or current is set in motion along the wire and then admit his inability to explain this so the physiologist physi-ologist must copfess his ignorance of someofthe details of the nervous telegraphy tele-graphy tof touqh However this we jlo know when I some of these bulbs are compressed pressure on the tip of thd finger the sensation of touch is sent coursing I through the hand the forearm and I arm across the shoulder under the collar bone to join with many others in that great highway to the nerves I the spinal cord and thus reach the brain It is not alone the Intricate and llttleI know mechanism of touch that is interesting inter-esting the different and remarkable manifestations in the various surfaces of the body and in the same surfaces in differfrit Individuals are equally so The curious tests and experiments with the sense of touch have been made mainly by the use of a very simple instrument in-strument devised by Drs Weber and Valentine This is a pair of compasses capable of fine gradual adjustment tipped with small pieces of cork If the points of the touchtesting instrument in-strument be applied to the centre of the back at very short distances apart the two sets of being but one point And this will usually be true in that region until the ponits are separated quite two inches A long serifs of experiments ex-periments made on many persons at all ages and under various conditions waranted Valentine in compiling the following table of distances at which the two r points maybe separately distinguished dis-tinguished On various parts of the body Tip of tongue 04 inch Tips of fingers average06 inch Under surface of middle joint of finger 13 inch Middle surface of tongun21 inch Back of fingers 32 inch Center of cheek 3S inch Back of handuo 5S inch Great toe 63 inch Instep 104 inch Over breast bone 132 inch Fleshy part of thigh 17S inch Middle of back 202 inch While these measurements do not give an absolutely correct idea of the II acuteness of touch they afford an ac I CorkTippecI Compass curate estimate of its delicacy and together with other experiments makeup make-up a fairly exact knowledge of the field The principal other experiments have to do with the different surfaces of the body as to the amount of weight that produces a change in tactile sensation The simplest apparatus for this purpose pur-pose consists of a pair of delicately poised balances so arranged that one arm can be brought to bear on any surface sur-face with a pressure varied by the addition ad-dition or subtraction of weights at the other end This instrument for testing the touch sensations of different weightS show that for the most part obtuseness to weight is found in the same areas and in about the same proportions as obtuseness to the other tactile sensation sensa-tion Thus we have the following delicate deli-cate changes in weight detected by the regions named Forehead and temples03 grain Fingers average 08 grain Chin and nose 62 grain After which come in order such areas as the back of the foot its sole the back of the legs and thighs and the middle of the back comes as the least sensitive In the light of these experiments we may readily understand why it is that a surface which feels smooth when passed a ross the back of the hand Is found to be quite rough if either the tip of the tongue or the index finger fin-ger is passed over It for the latter have fully 140 times the sensitiveness of the former So too we can understand why a blow on the back is far less painful than one on the top of the great toe and realize why the usual method of spanking is much preferred by the spanked one to the application of a ruler across the fingers and palm It must be borne in mind that the figures here given are for an average of different ages and varying conditions condi-tions When we compare individuals we find some very surprising differences Even among children of the same parentage marked differences may be observed as anyone may prove by trying the compass experiments among his acquaintances ac-quaintances When it comes to different classes of o 0 I00 OIpOi ciui 00 t I 4 L u 1 Deseciion of Tongue 2 Actile Corpuscle the same race the differences are more marked The tactile sense is then seen to be one susceptible of much cultivation cultiva-tion one as capable of training as sight or hearing or as improvable by use as the muscles of the arm For example the sensibility in the finwer tips of a blind person trained to read raised letters with them is many times more acute than that of a sailor whose fingers fin-gers have grown callous by exposure and work So too the arm of a young I girl tender and soft is far more sensitive sen-sitive to touch than that of a foundry man whose muchthickened skin has I oyffered the hardening effect of great neat Naturally as tactile sensibility depends de-pends on how close together are placed the papilla containing nerve bulbs it is correct to reason that pain is acute in proportion to the frequency of these in any area This we find to be the case The acheing tooth or ear the pain from a splinter under a finger nail an injury in-jury to the tongue or eye are all exceedingly ex-ceedingly painful because they involve a region where nerve terminals are thickly placed A boil on the palm t of the hand will involve fully 250 times as many sensative points as will one in the middle of the back simply because be-cause 13 is but onesixteenth of 202 and the square of 16 Is 256 And this brings us to a most surprising sur-prising fact By many measurements and experiments made by Professor Lombroso and others it is ascertained ascertainedr that the average of tactile sensibility in woman is considerably less than in mare Sence we are compelled to reconsider re-consider the longheld theory that woman wo-man makes less display of suffering because she possesses greater fortitude forti-tude greater mental control under agony ag-ony Professor Lombroso and a number num-ber of foremost physiologists now believe be-lieve that woman has been endowed L < I with somewhat less sensibility to pain as a kindly provision of nature sInce she is called on to suffer so much Be that as it may we can as we lay 1 our papers down now understand how it is that they make so much less impression im-pression dropped into our laps than r they did held in our hands t |