Show 1 st How Hw Y au Get iY Your our Sense of Touch The Termination of a Nerve Nerve 32 t in a Touch Corpuscle i Micrometer and Probe Used A for Testing It by Means leans of d 11 Which hick Differences of 1 Inch Can Be Detected D x 1 FIG 1 FIG 2 FIG 3 FIG 4 FIG 5 Heat Spots on a Small Portion of the Palm of the Hand Are Shown by the Shaded Areas Area Cold cold Spots The Spots The Blackened Areas Arc Are More lore Sensitive Than the Lined Portions and the Afore alore Sensitive Than the tho Dotted Ones FIG 3 A 3 A Hair Bair Mounted on a Wooden Handle with pf f Sealing Wax Vax for Determining the Minimum Amount of Pressure Necessarily Applied fit f Sensation Is Evoked FIG 4 4 Method Method of Determining the Amount of Pressure Produced Hair glair by Pressing It Down Into One Pan of a Delicate Balance The Hair flair Bends and the Bending Gives the Degree De e of of Pressure Presure Applied by the Hair lIah FIG n A 5 A Draftsman's Comte Com Com- lending te ted with Two Cork Cork Tips Tip Enables the Experimenter to to Determine e the the Distance Between the te Points Necessary to Produce the Sensation of Discrimination micrometer Is so marvelous an nt that differences of one one one-one hundred hundred- of an an inch can be dete detected ted But Butres res es in your tips finger-tips are so sensitive e ey y can actually check up on the accuracy rometer ameter accuracy nc with th which the nerves nerv s' s in the th s swill will record small differences in inn dimen dimen- I Jends ends on n various factors The h human n nn Rina and n the thickness of the skin affect the to some extent and so does the weight eight weight and the roughness of surface of let ct felt Ordinarily with small objects pound or so in weight and a few inches h 1 a disc discrepancy of a thousandth of an anIbe anbe an anbe Ibe be readily detected Under proper cires cir cir- es however it is possible to exceed this when the surfaces are polished and of ofas tes e-as as with small steel balls the fingers Sice ce- ce differences of a thousandth hundred-thousandth chi ch thod of demonstrating the sensitiveness is explained in Popular Science Monthly Briggs who used a machinist a thin aluminum handle in which ai a ai i set at each end end as shown in o one e of illustrations In a well made I ter the faces on the spindle and the anat an an- at t and perpendicular to the axis of the with an accuracy of between ten one lih ten one and one-one one thousandth hundreds of With a micrometer that is new or in ina Edition a lion it is possible to adjust the dis- dis tWeen the measuring faces so that the K probe will just be held in place se senses ses which you perceive through your numerous and varied such as those sev sev- of sensation relating to the sense and including that of discrimination the and the sense of pain A investigation of the skin surface bears idea that these three great classes of Rj ISI skin sensations have special cl classes of mechanisms for each individual these senses it is best to take taka Band and deal with each separately Through Ecy cy cr of the skin and the touch-corpuscles touch able to perceive various qualities such as texture and hardness of the objects ts in WIth the skin Of course the sense of s also has associated with it a muscular A S Section of the Human r Skin Highly q Magnified and One s of f the r Touch uch Corpuscles sense in that you are able to tell the hardness of the he object by pressure But the real sense sense sense-of of touch can be easily found and so can the location of the touch spots by the following very simple experiment which Joseph H H. Kraus describes in Science and Invention If a hair hait is mounted on a wooden handle with witha a small piece of sealing wax and the skin pressed with this hair until the hair bends then a certain known pressure is being applied to the skin The T he heskin heskin skin is then hen gone over carefully with this hair nair and wherever a touch sense is indicated and the hair is felt touching the skin a tiny cross or dot dotis dotis dotis is placed on a chart The pressure applied by the hair is then determined determined determined de de- de- de by pressing down upon a balance which will register the number of pressure grams-pressure a hair of that thickness can give because the hair will bend at a certain point and the point of bending bending bending bend bend- ing will wil give the weight the hair is capable of applying Kj It appears to matter very little whether r the surface of the skin is pushed downward or pu pulled led upward by an instrument A sense of pressure in either case is announced to the brain train Scientists Scientists I find that on the tongue and anCl nose a pressure pressure pressure pres pres- sure of only two grams per square millimeter will announce to the brain that a certain region is is' being touched On t the e back of the forearm it requires a BALL tG 1 1 g I pressure of 33 grams per square millimeter and andon on the back of a finger only five grams Nearly all pressure sensation l localizes itself near a hair root and in particular on the side opposite to the direction toward which the hair slants The sense of touch is greatly augmented by bya a profusion of hair on the skin says Mr Kraus When a slight touch is applied to the hair proper prop prop- er er it acts on the long lever arm of the hair and multiplies the force of pressure so applied five or more times because the hair is pivoted at the surface of the skin and the small arm of the lever projects through the skin into a hair follicle profusely surrounded by nerve endings It has been found that before the skin was shaved 2 milligram pressure was effective whereas after being shaved it t required a 36 milligram pressure to produce the same feeling of touch A different sense is that of dl discrimination crimination or what is otherwise known as the spatial quality of touch If any part of the skin of the body is stimulated by applying a cork point to the skin you can instantly tel tep the exact location of the excited spot If now instead of one point two cork points are substituted in a pair of dividers there must be a certain spatial distance distance between between these points varying in different parts of the body before you rou are able definitely to determine whether or not there there are two points or only one point in contact with the skin By the temperature senses the skin can appreciate that a body coming in contact with it is either cold or warm wann If the body is is of the same temperature as the skin no sensation is generally excited Neither are the senses of warmth and cold produced by the same means The experimenter can readily determine this for himself by warming a small small- pointed glass rod and passing it over the palm of the hand Certain regions in the hand will then give a sense ense of warmth Others give a medium sense while in still other spots no sensation will be evoked by touching the skin with the glass rod If a rod is on the other hand cooled to a n few degrees below body heat and moved over the same regions cold spots can be definitely out out- lined An investigation of these warm and cold spots says Mr Kraus shows that the apparatus apparatus apparatus ap ap- ap- ap for the appreciation of cold is much mare distributed over the body than that of warmth The cold areas are best marked on the chest the nose the abdomen etc and both cold and heat are less sensitive on th the face hands and mucous membranes We c can n therefore drink hot drinks which if applied to tho the hand and other more sensitive parts of the body would prove very painful When the skin is very cold or very hot it is much more difficult to recognize a change of temperature |