Of examples may be mentioned the frowns, dilated nostrils, and stampingsof anger; the contracted brows, and wrung hands, of grief; the laughs andleaps of joy; the frantic struggles of terror or despair. Passing over casesin which extreme agitation causes fainting, we see that whatever be the kindof emotion, there is a manifest relation between its amount, and the amountof muscular action induced, from the fidgettiness of impatience up to thealmost convulsive movements accompanying great mental agony. To these severalorders of evidence must be joined the further order, that between feelingsand those voluntary motions which result from them, there comes the sensationof muscular tension, standing in manifest correlation with both -- a correlationthat is distinctly quantitative: the sense of strain varying, other thingsequal, directly as the quantity of momentum generated. §71a. But now, reverting to the caution which preceded these twoparagraphs, we have to note, first, that the facts do not prove transformationof feeling into motion but only a certain constant ratio between feelingand motion; and then we have further to note that what seems a direct quantitativecorrelation is illusory. For example, tickling is followed by almost uncontrollablemovements of the limbs; but obviously there is no proportion between theamount of force applied to the surface and the amount of feeling or the amountof motion: rather there is an inverse proportion, for while a rough touchdoes not produce the effect a gentle one does. Even when it is recognizedthat the feeling is not the correlate of the external touching action butof a disturbance in certain terminal tactile structures, it still remainsdemonstrable that there is no necessary relation between the amount of suchdisturbance and the amount of feeling produced; for under some conditionsmuscular motion results without the intercalation of any feeling. When thespinal cord has been so injured as to cut off all nervous communication betweenthe lower part of the body and the brain, tickling the sole of the foot producesconvulsion of the leg more violent than it would do were it accompanied bysensation: there is a reflex transmission of the stimulus and genesis ofmotion without passage through consciousness. Cases of another class showthat between central feelings or emotions and the muscular movements theyinitiate there are no fixed ratios: instance the sense of effort felt inmaking a small movement by one who is exhausted, or the inability of an patientto raise a limb from the bed however strong the desire to do it. So thatneither the feelings peripherally initiated nor those centrally initiated,though they are correlated with motions, are quantitatively correlated. Evenstill more manifest becomes the lack of direct relation, either qualitativeor quantitative, between outer stimuli and inner feelings, or between suchinner feelings and muscular motions, when we contemplate the complex kindsof mental processes. The emotions and actions of a man who has been insultedare clearly not equivalents of the sensations produced by the words in hisears for the same words otherwise arranged, would not have caused them. Thething said bears to the mental action it excites, much the same relationthat the pulling of a trigger bears to the subsequent explosion -- does notproduce the power but merely liberates it. Whence, then, arises this immenseamount of nervous energy which a whisper or a glance may call forth?
Evidently we shall go utterly wrong if the problem of the transformationand equivalence of forces is dealt with as though an organism were simpleand passive instead of being complex and active. In the living body thereare already going on multitudinous transformations of energy very variousin their natures, and between any physical action filling on it and any motionwhich follows, there are intercalated numerous changes of kind and quantity.
The fact of chief significance for us here, is that organization is, underone of its aspects, a set of appliances for the multiplication of energies-- appliances which, by their successive actions, make the energy eventuallygiven out enormous as compared with the energy which liberated it. A physicalstimulus affecting an organ of sense, is in some cases multiplied by localnervous agents; the augmented energy is again multiplied in some part ofthe spinal cord or in some higher ganglion; and this usually again multipliedin the cerebrum and discharged to the muscles, is there enormously multipliedin the contracting fibres. Of these transformations Only some carried oncentrally have accompanying states of consciousness; so that, manifestly,there can be no quantitative equivalence either between the sensation andthe original stimulus, or between it and the eventual motion. All we cansay is that, other things equal, the three vary together; so that if in onecase successive stages of increase are 1, 9, 27, 270 they in another casebe 2, 18, 54, 540. This kind of correlation is all which the foregoing factsimply. But now let us glance at the indirect evidences which confirm theview that mental and physical forces are connected, though in an indirectway.
Nowadays no one doubts that mental processes and the resulting actionsare contingent on the presence of a nervous system; and that, greatly obscuredas it is by numerous and involved conditions, a general relation may be tracedbetween the size of this system and the quantity of mental action as measuredby its results. Further, this nervous apparatus has a chemical constitutionon which its activity, depends; and there is one element in it between theamount of which and the amount of function performed, there is an ascertainedconnexion: the proportion of phosphorus present in the brain being the smallestin infancy, old age, and idiotcy, and the greatest during the prime of life.
