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Show ~Hin p1ttN01PLln OF dnAt\ 1. g() ment Yet if a drop of consciously perform, an~ mo;esurfa~e of the thigh of a acid be placed o~ th?ll ow: ff the drop with the upper fro()' in this state, It Wl ru 0 leg If this foot be 0 h £ t of the same · surface of t e 00 t "After some fruitless efforts, cut off, it cannot thus ac . t . g 1.11 that way, seems 't . s up ryin ,, therefore, I give Pfl" ger it was seeking some " restless, as though, say~ ~~ s ~se of the foot of the " other way, and at last .1 ~~b:n off the acid. Notably " other leg and succeeds~~ I tr~ctions of muscles, but "we have here not mere y con t' ·n due sequence 1 · ed contrac 1ons I ,, combined ~nd larmon~z rrbese are actions that have " for a special pnrpos b. . . led by intelligence and " 11 th earance of eing guic . a . e a pp . . . 1 the recoo-nized orgau . . t d by Will In an anima ' o d "Io " Instiga e . . d will has been remove . '' of whose Intelligence an fl d voluntary We see the difference betwee~l re ex an b . able . . oung children not eing 111ovements In vety ! £ d b Sir Henry I-Iolland, !' • as I am In orme Y . to perioim, 1 us to those of sneezmg certain acts somewhat ana o~o b . ble to blow · 1 · their not e1ng a and coughing, name y, In th se and blow violently their noses (i.e. to comp~e~s l e.~o .. t being able to clear through the passage), an In t leu not learn to perform their throats of phlegin. They have 0 · 1 little these acts, yet they are performed by ':s, w le~:eezino older, almost as easily as reflex n~~~~~~~· by the will and coughing, however, can be co l : fl the . t 11. whilst the c earmo only partially or not a a ' 1 t 1 under our throat and blowing the nose are com P e ·~ y comn1and. f an irritating When we are conscious of the presence o ~ h the particle in our nostn·l s or wi· n d pi· pe........... that. I S; hw ceans e of same sensory nerve-cells are excited, as ~~I ex el the sneezing and coughing-we can voluntarl y e p ·---~----- · 1 ' 1s·o p· to Dl'. ~Iandsley, ' nody and :Mml , 1 ' • s~ CHAP. I. SERVICEABLE ASSOCIATED HABITS. 37 particle by forcibly driving air through these passages; but we cannot do this with nearly the sa1ne force, rapidity, and precision, as by a reflex action. In this latter case the sensory nerve-cells apparently excite the motor nerve-cells without any waste of power by first communicating with the cerebral hernispheres-the seat of our consciousness and volition. In all cases there seems to exist a profound antagonism between the sarne movements, as directed by the will and by a reflex stiinulant, in the force with which they are performed and in the facnity with which they are excited. As Claude Bernard asserts, " L'infiuence du cerveau tend " done a entraver les mouvements reflexes, it limiter " leur force et leur etendue." 11 The conscious wish to perform a reflex action sometimes stops or interrupts its performance, though the proper sensory nerves may be stimulated. For instance, many years ago I laid a small wager with a dozen young rnen that they would not sneeze if they took snuff, although they all declared that they invariably did so; accordingly they all took a pinch, but from wishing much to succeed, not one sneezed, though their eyes watered, and all, without exception, l1ad to pay Ine the wager. · Sir H. Holland re1narks 12 that attention paid to the act of swallovt'ing interferes with the proper movements; fro1n which it probably follows, at least in part, that some persons find it so difficult to swallow a pill. Another familiar instance of a reflex action is the involuntary closing of the eyelids when the surface of the eye is touched . . A similar winking 1novement is caused when a blow is directed towards the face ; but 11 See the very interesting discussion on the whole subject by C1nuclo Bernard, 'Tissus Vivants,' 1866, pp. 353-356. 12 'Chapters on Mentftl Physiology,' l858, p. 85. |