CHAP. IX. SECT. III. EXTERNAL *SENSES, &c. Of the external senge ses in neral.(b) Importance of the SECT. III.-OF THE EXTERNAL SENSES, THEIR ORGANS AND PARTS. The External Senses (as distinguished from the Mental) are those faculties of the body which enable the mind, or the internal senses, to have communication with external objects, and are the media through which we receive simple sensations, which are the first elements of our thoughts, and the means of developing all the powers of the understanding. They exist, more or less, as well in animals as in man, and sometimes even superiorly in the former, though, upon the aggregate, man, by the additional power of communicating his ideas with his fellow creatures, by the intervention of speech, and by his superior mental faculties, can in general better apply each external sense.(c) It has been justly observed, that the agency of the senses, the intercourse between the mind and external matter, and the influence of the mental will over the body, are mysterious; and notwithstanding all the seeming confidence of those who have written upon the subject, seem still to be inexplicable phenomena:(d) Next in importance to the intellectual powers of the mind, the knowledge of the external senses claim the most interested attention; because knowledge of the exit is now clearly established, that the mind can only exercise its powers ternal sen- through and by means of the external senses, for all our acquired mental ses, as well perceptions are originally derived from impressions made on our external legally as senses, and from thence conveyed to the Sensorium, or at least to some medically. part of the brain; and when we abstract or generalize our ideas, we do so by comparing and combining the knowledge we have derived from such external senses.(e) Bereft of the organs of hearing and speech, it will be found that the knowledge and attainments of individuals would be lamentably limited;(f) and if all the external senses should be destroyed or rendered inactive during infancy, or before ideas of external objects have been impressed upon the mind, there would be no mental intelligence whatever. It is needless to enlarge upon the necessity for an accurate knowledge of the external senses to the practising physician;(g) and it has been justly observed, that a knowledge of the nature of the union between the mind and body, is of the greatest practical importance in the administration of justice, especially as regards evidence, and as the (b) See division of the subject, ante, 243. We have seen that the nervous system or function embraces the external organs of sense, ante, 244, 245; and see 2 Bell, 364; 2 Par. & Fonb. 25 to 31; G. Smith, 33, 34, 219; 4 Good, 1 to 32; 1 Dungl. Phy. 73 to 225. (c) See, in general, 4 Good, 1, 9, 13 to 17. (d) See Amer. Cyclop. Prac. Med. tit, Age; 3 Bell, 2; 4 Good, 39; 3 Bost. 147 to 160. (e) See Locke and Berkeley, and other authorities; 3 Bost. 147 to 160; Stewart's Elements, vol. 1, sect. 4, p. 99; 1 Dungl. Phy. 247 to 281. (f) Post. (g) Dr. Gregory on Duties of a Physician, 93; and 3 Bost. 145. following observations and the numerous cases relative to the identity of CHAP. IX. persons and evidence in general will establish. (h) SECT. III. EXTERNAL &c. tion of the external senses, viz. The external bodily senses, as distinguished from the mental or in- SENSES, ternal, are Sight, Hearing, Smell, Taste, and Touch. (i) Four of these are situate in the head, and some of the cerebral nerves, already con- Enumerasidered, constitute parts of the instruments of those senses. The fifth sense (touch) is situate nearly every where in the external parts of the frame, though by the habitual use of the fingers, the sensation is in them sight, hear more acute, delicate, and perfect, than in other parts of the frame. (k) ing, smell, To these five senses it has been suggested that a sixth might be added, taste, namely, the sense of Motion, for it is by a sense of motion that we know touch, momany of the qualities of outward things, as their distance, shape, resist- tion, ance, and weight; and speech and voice have been treated as a seventh speech, sense,() but they are rather modes of relating, communicating, or receiving ideas of other senses, than as constituting in themselves a distinct sense. It has been observed, that the existing causes of all external senses act by what may be regarded as a species of touch, for the rays of light strike the retina of the eye, the undulations of the air, constituting sounds, communicate their motions to and vibrate in the interior of the ear, the sense of smell is produced by particles emitted from the odorous body, and carried by the air to the nose, while taste is immediately caused by the contact of the sapid body with the papillæ of the tongue.(m) and voice. The office of the nerves, which we have considered, is to convey the Internal impressions of the external senses to the sensorium of the brain, where, senses. by a process as yet not satisfactorily established, representations are made to the mind. We know little further than that by the operation of the mental perceptions and powers, new thoughts are excited in the mind. (n) With respect to the Internal senses, being those of the Mind, they are usually enumerated as perception, memory, association, comparison, imagination, reason, and judgment, (o) to which several others may be added. All sensations originate in the external senses or organs receiving the impressions of outward bodies. When this change influences the mind, we call it Perception; Memory is the power of recalling these sensations; and Imagination is the power of suggesting new combined ideas, and termed the mother of Invention. They are powers of the mind, which by the constitution of our nature are gradually acquired and increased by due exercise. In infancy the perceptions are simple and transitory; Memory is only perfected by degrees, whilst by the accumulated store of ideas, the imagination is invigorated, but still it is kept limited to the ideas received, not from, but in consequence of the operation of the external senses.(p) Strength of Mind and Judgment are, however, acquired not so much by an accumulation of new ideas, as by reflection upon and comparison of those ideas which we have already attained. (q) (h) See post, and 1 Beck, Med. Jur. 224 to 233. (i) 4 Good, 42; 3 Bell, 1 to 235; 1 Dungl. Phy. 71. (k) 3 Bell, 1 to 10. By a change of habit, the sense, as well as muscular power, may be transferred to another part; as in the well-known instance of the female, who, having lost her arms, has cut out, most dexterously, watch papers, and made lace by the use of her toes. (1) 3 Bell, 6, sed quære. In Com. Dig. Idiot. (B.) it is supposed that if a CHAP. IX. Conse quence of the loss or absence of one or external senses. It has been observed, that individually no one of the external organs SECT. III. of sense, by itself, conveys much information to the mind, (r) and that EXTERNAL the loss of one of the senses after it has been fully exercised, at least in SENSES, early life, will sometimes be providentially, in a considerable degree, &c. compensated by the others becoming stronger and more acute.(s) But with the exception that if a person be born totally deaf, it follows that he must be also necessarily dumb (or rather his power of articulation will be suspended whilst he continues dumb,) because as he could never have the use of heard any sound, he could not, by articulation, imitate the language of others, which is the only source of speech.(1) Whilst, on the other hand, more of the the loss of one or more of these senses in later life, after a long exercise of the whole, will leave the individual in full enjoyment of many faculties of the mind, and especially those of memory and imagination, although he may be incapable of increasing the store of images and ideas. It has been observed that where one of the senses is deficient, and especially when naturally so, the rest have very frequently been found in a more than ordinary degree of vigour and acuteness, as though the sensorial power were primarily derived from a common source, and the proportion belonging to the organ whose outlet has become destroyed or imperfect, were distributed amongst the other organs.(u) But it has been judiciously remarked, that whether that principle be true or not, it is more certain that another principle is generally concerned, resolvable into attention, habit, or practice. Thus a blind man whose eyes cannot apprize him of danger, or convey to him any kind of information, is habitually all attention with his ears, just as the organ of touch in a deaf and dumb person is, from necessity, continually exerted and brought by habit to acquire a more exquisite power of feeling and discrimination far superior to what is enjoyed by the generality of mankind.(x) But it is supposed that perfect quickness of perception and mental intelligence can only be attained by the possession of all the five senses, because it is by comparison and combination of all the several simple and original affections or feelings conveyed to the sensorium, and by their being associated and combined to infinity, that they administer to the memory and imagination, to taste, reasoning, and moral perception, and every active power of the mind. (y) And it has been observed, that if an individual were from his birth, deprived of the use of all his external senses, possessing no faculty of seeing, hearing, tasting, smelling, or discrimina (r) 3 Bell, 10, 105, 106, 128. (s) 4 Good, 159; 3 Bost. 129, as to the singular delicacy of touch, and still more of smell in persons born deaf, and consequently dumb. (t) 1 Par. & Fonb. 371, where see the detection of an imposture by applying this rule. M. Sicard, it is said, succeeded in detecting a most accomplished impostor, who pretended to have been born deaf, and therefore, dumb, by requiring him to answer a number of queries in writing; when the Abbé soon found that he spelt several words in compliance with their sound, instead of according to their established orthography; as by substituting, for instance, the c for the q, which at once enabled the Abbé to declare that it was impossible that he should have been deaf and dumb from his birth, because he wrote as we hear, and not as in the case of the real deaf and dumb, sed quære, If he might have been taught to write by an illiterate person, and therefore, spelt incorrectly, without ever hearing. Milton, who wrote so feelingly of his own loss of vision, had been born blind; he could not have described and pictured so luxuriantly the beauties of creation, particularly the sun, nor described woman in the person of Eve. "On she came; grace was in every step; Heaven in her eye; in every gesture, dignity and love," (u) 4 Good, 139; G. Smith, 437, to 430. (x) 4 Good, 139, in note; G. Smith, 437; and see an interesting case, Coop. Surg. Dict. 337, of a deaf and dumb girl discovering the opening of a distant door, merely by the tremulous effect upon the chair in which she sat. (y) 3 Bell, 10. tion by touch, he would perhaps amount to no more than a growing mass of organized matter as respected his relative situation in life, in short, a mere automaton; though if having fully exercised those faculties for a time, he should afterwards lose the power, his intellectual vigour and experience might in all probability enable him to carry on his social functions, at least in some degree. (z) If a person be born deaf, it is considered that he must of necessity be dumb; but there is not necessarily, on account of deafness, any defect in the organs of speech, but the power of exercising it is merely suspended during the continuance of the deafness, by the circumstance of the individual never having heard sounds, and consequently being unable to imitate them; and speech is merely the imitation of certain tones and words previously uttered by others. If the sense of hearing were established, then immediately the power of speech might be exercised; yet the law has erroneously supposed that a man who is born deaf, dumb, and blind, must be in the same state with an idiot, and he is supposed incapable of any understanding, as wanting all those senses which furnish the human mind with ideas. (a) It has, however, been decided in more modern times, that a person deaf and dumb is not on that account incompetent, but if he have sufficient understanding, may give evidence by signs, with the assistance of an interpreter; (b) and the astonishing intelligence evinced by persons, who have been under the care of the Philanthrophic Deaf and Dumb Asylum, fully proves that although some of the organs of external sense may be suspended, or even destroyed, yet the mind is still capable of very considerable cultivation.(c) We shall, in a following section, consider the practical application of this subject. Considerations of this nature are not only important to medical prac titioners, but essential as regards every department of medical jurisprudence, especially that branch termed Medical Police, and indeed as regards every member of society, in all questions of disabilities or disqualification for evidence.(d) Thus in legislating or prescribing punishment or compensation for any injury to one or more of the organs of sense, legislators, judges, barristers, and juries ought to be well informed of and be able justly to appreciate the ultimate consequences to the suffering individual; and though the absurd lex talionis does not prevail in this country, (d) yet as the practice of the judge's increasing damages for wounds and injuries super visum vulneris is not in use, (e) it has become of essential importance that all concerned in the administration of justice should be able accurately to anticipate and estimate the actual and probable final consequences of all injuries to these organs of sense.(f) CHAP. IX. SECT. III. EXTERNAL &e. The several external senses and their organs are usually thus arranged: The seve1st, Sight; 2dly, Hearing; 3dly, Smell; 4thly, Taste; 5thly, Touch and ral senses (z) G. Smith, 137. (a) Co. Lit. 42; Fleta, lib. 6, c. 40; 1 Bla. Com. 304; post. (b) Ruston's casc, 1 Leech's R. 408; post. (c) See Ency. Brit. vol. iii. Supplement, tit. Deaf and Dumb; and Stew. Phil. vol. iii. 401; also, Hoffbauer, Med. Legale. (d) G. Smith, 437 to 439; see 4 Bla. Com. 13, cites Pott's Ant. b. 1, c. 26, where, in speaking of the lex talionis, it is observed, that the law of the Locrians, which demanded an eye for an eye, was judiciously altered, by decreeing that he who struck out the eye of a one-eyed (e) 1 Ld. Raym. 176; 3 Salk. 115; (f) Thus, supposing upon the trial of an action for a battery, in consequence of which the eyes or ears are, at the time of the trial, in an imperfect state, if the jury should be satisfied that the plaintiff will, probably, never recover the use of his eyes, should not the damages be greatly enhanced? separately considered. CHAP. IX. Feeling. To these, as we have seen, many may be added: 6thly, The SECT. III. sense of motion;(g) and 7thly, the sense of speech and voice.(h) These EXTERNAL several senses have been either collectively or separately the subject of very numerous interesting works.(i) We shall here only notice the leading points most important in medical jurisprudence, with a few explanatory plates. SENSES, &c. First, Of sight and its organs, the eyes. The eye is an optical instrument, so constructed as to convey the impressions of objects placed in front of it to the retina, or expansion of the optic nerve at the posterior part and sides of the eye, and by which they are carried to the sensorium. By a simple and well understood principle of optics, the rays of light, reflected from any object which they carry to the eye, when the eyelid is raised or open, first impinge or fall upon the cornea, which extends in front of the iris and pupil, and are refracted by it in such a manner as to diminish the circle which they form in front; and in which contracted state they pass through the pupil, which is merely the opening of the iris, and which is enlarged by the radiated, or contracted by the circular fibres, in proportion to the intensity of the light required by the retina. Having passed through the pupil, the rays of light are received on the crystalline lens or humour, which resembles in colour the brightest glass, and in shape is similar to a double convex glass or optician's lens, and by which they are drawn to a point or focus, at a certain appropriate distance behind it, and at that distance is placed the retina. In traversing the eye, some of the rays are scattered in various directions, and these are absorbed by the dark pigment or black coloured fluid which is secreted by the choroid membrane surrounding the inner part of the eye. The object is delineated on the retina, (in concert and sympathy with which the iris acts,) and its impression is transmitted by the optic nerve to the brain, which is thus rendered sensible of the existence of the object upon the retina. In consequence of the decussation of the rays within the eye, all objects are inverted on the retina. But as the retina possesses the power of determining direction as well as distance, and as the mechanical condition of the function stops at the retina, and the transmission of the object along the optic nerve, is a vital not a mechanical phenomenon, it would be idle to argue against the opinion now obsolete, that habit alone enables us to overcome the visual defect. (i) The following figures will assist in explaining, though they are not minutely accurate.(j) (g) 3 Bell, 10. iii. 61 to 136; 1 Dungl. Phy. 70 to 228; (h) 3 Bell, 6; quære, see ante, 287, Jackson, Prin. Med. 143 to 171; Brous. note (k.) (i) See, in general, 3 Bell, 1 to 235; 4 Good, 1 to 32; id. 197 to 323; 138 to 212; and the observations of Dr. Bostock, vol. Phys, 66 to 91; see, further, Newton's Optics; and 1 Dungl. Phy. 182, &c. (j) A diagram on a large scale, with explanation, may be purchased of Messrs. Carey & Hart, &c. |