Ambidexterity

“ Cælius Rodiginus undertaking to give a reason of Ambidexters and Left-handed Men, delivereth a third opinion: Men, saith he, are Ambidexters, and use both Hands alike, when the heat of the Heart doth plentifully disperse into the left side, and that of the Liver into the right, and the spleen be also much dilated; but Men are Left-handed when ever it happeneth that the Heart and Liver are seated on the left-side; or when the Liver is on the right side, yet so obducted and covered with thick skins, that it cannot diffuse its vertue into the right. ”

“ Some people, however, are as we say, ambidextrous; that is, they use both hands about equally well, just as all animals do. Nobody, however, is ever naturally ambidextrous. Sometimes the ambidexters are people who have hurt the right hand, and had to learn to use the left. ”

“ Man was once, in his childhood on earth, what Charles Reade wanted him again to be in his maturer centuries, ambidextrous. And lest any lady readers of this volume—in the Cape of Good Hope, for example, or the remoter portions of the Australian bush, whither the culture of Girton and the familiar knowledge of the Latin language have not yet penetrated—should complain that I speak with unknown tongues, I will further explain for their special benefit that ambidextrous means equally-handed, using the right and the left indiscriminately. ”

“ Figure 19.—A record plotted from the data of one experiment. The time intervals in hours and minutes are represented on the abscissa; the values of the threshold in β units are represented on the ordinate. The continuous line is the record of the muscle, the broken line that of the nerve-muscle. The nerve-muscle record is magnified 100 times; that of the muscle is normal.
(1) Normal threshold stimulus. (2) Threshold five minutes after an intravenous injection of 0.1 cubic centimeter of adrenin (1:100,000) without previous fatigue. ”

“ It is rare that you meet a person who is ambidextrous,—that is, who uses both hands equally well. When, therefore, he sets out to travel through the woods without any guide, he unconsciously exerts his right or left limb, as the case may be, more than the other, and this makes his course circular. ”

“ But some ambidexters, oddly enough, are made so by an injury to the sight of the right eye, if they were right-handed to begin with, or to the left eye if they were left-handed. Hand and eye have so often to work together and work quickly, that one tends to use the hand on the side of the better eye, even when that is the wrong side.
At any rate, tho it is an excellent plan to learn to do all heavy work equally well on either side of the body and with either hand, fine work and quick work and thinking work had better be done with the hand that does it most naturally. ”

“ Very few are ambidextrous. We unconsciously allow for this condition in our daily walks and movements, since we are surrounded by landmarks as may be said; but when these aids are removed, we are swayed by the muscles on one side more than by those on the other. A right-handed person unconsciously verges to the left, while the left-handed one does the opposite. The impulse being uniform, even if slight, his course naturally assumes the form of a circle.
It was hardly to be expected that Mike Murphy should reason out this explanation, for he had never before experienced anything of the kind. ”

“ Few persons are ambidextrous. Many more might use the hands with equal skill, if they would. Even so simple an operation as putting on a coat, using the wrong arm first, or buttoning a vest with the other hand, is awkward for most persons, and [135] quite difficult to many. ”

“ That there is in amber something flammable or something having the nature of breath, and this by the attrition of the surface being emitted from its relaxed pores attracts bodies. And if it be an effusion does it seize upon the air whose motion the bodies follow, or upon the bodies themselves? But if amber allured the body itself, then what need were there of friction, if it is bare and smooth? Nor does the force arise from the light which is reflected from a smooth and polished body ”

“ In the second part, there is a rapidly increasing effect with increased stimulus. Finally, a tendency shows itself to approach a limit of response. Thus we find the curve at first slightly convex, then straight and ascending, and lastly, concave to the abscissa (fig. 30) .
In muscle the limit of response is reached much sooner than in nerve. As will be seen, the range of variation of stimulus in these curves is not very great. When the stimulus is carried beyond moderate limits, the response, owing to fatigue or other causes, may sometimes undergo an actual diminution. ”

“ If, therefore, we ever solve the mystery of dextrality and sinistrality, it will be by the study of the conditions, habits, necessities, etc., of the ancestral types when dextrality and sinistrality arose. The infant of a few months shows no signs of preference in the use of the hands; it is not yet dextromanual, nor ambidextral; it is simply nondextrous, or ambisinistrous. Almost as soon as it exhibits any conscious effort toward skillful use of the hands it begins to show signs of dextromanuality. Before it walks, before it is one year old, dextrality is clearly pronounced. ”

“ Although unable to trace the connection by which a disordered state of the stomach and bowels may induce a morbid action in a part of the medulla spinalis, yet taught by the instruction of Mr. Abernethy, little hesitation need be employed before we determine on the probability of such occurrence. The power, possessed by sympathy, of inducing such disordered action in a distant part, and the probability of such disordered action producing derangement of structure, can hardly be denied. ”

“ If, therefore, the wave of excitation, coming from above, is obliterated exactly at the same point, whether brought about by weak or strong stimuli, the inevitable conclusion must be drawn that, whether either a weak or a strong stimulus is operative, the wave of excitation must have entered into the influenced stretch from the normal stretch with exactly the same intensity. In other words: the weakest as well as the strongest stimuli produce excitations of equal intensity in the normal nerve, that is, the “all or none law” is valid for the nerve. ”

“ Deep in the loins there has been the smouldering fire of disease, which is to result in what is called "Lumbar abscess." This grievous malady, which in many instances begins not less insidiously than I have mentioned, is found on inquiry not to have been wholly without some of those premonitory signs which, in obedience to the beneficent57 laws of the animal economy, almost invariably precede even the most insidious malady. Inquiry generally elicits that, however little complained of, there has been at times more or less of uneasiness, if not pain, felt in the loins ”

“ Abduction is the relative power of the external muscles to turn the eyes outward. Prism power base in and apex out is employed. To determine abduction, or the amount of divergence of the external rectus muscle of the right eye, prism power with base in or toward the nasal side should be employed. The rotary prism will therefore remain in the same relative position as in making the adduction test (Fig. 22) , with the two cyphers (0) or zero graduations vertical, but the indicator or red line should be rotated inward from zero, or towards the patient’s nose. ”

“ In those who are subject to diabetes and dropsy, the absorbent vessels are naturally more irritable than in the latter; and by being frequently disturbed or inverted by violent stimulus, and by their too great sympathy with each other, they become at length either entirely paralytic, or are only susceptible of motion from the stimulus of very acrid materials; as every part of the body, after having been used to great irritations, becomes less affected by smaller ones. ”

“ Now the further point, which, as we would contend, time and labour have supplied, is first this—that what Hunter had mentioned as one feature in the history of the sympathies of different organs, and Abernethy as an occasional or not unfrequent occurrence, is, in disorders of any standing, and with the exception of mechanical injury, in fact the rule—the symptoms of disorder being almost never in the primary organ; nay, even organic change (disease) is for the most part first seen in a secondarily affected organ. ”

“ Furthermore, many aggregates whose arousal could otherwise be easily effected by the given stimulus may temporarily be in a condition in which their thresholds have become raised and thus fall outside the sphere of activity of the functioning aggregate. On the other hand, aggregates that are usually inaccessible to those minimal stimuli may under certain conditions be set into activity by minimal stimuli, if there is a lowering of the threshold of the total aggregate. Thus the aggregates set into activity by the functioning aggregate are conditioned by the rise and fall of their thresholds. ”

“ Thus, for example, when the nerves of the foot are violently or more than usually shaken, the motion passing through the medulla of the spine to the innermost parts of the brain affords a sign to the mind on which it experiences a sensation, viz, of pain, as if it were in the foot, by which the mind is admonished and excited to do its utmost to remove the cause of it as dangerous and hurtful to the foot. ”

“ I have in the preceding paragraph described an experiment where under a given intensity and duration of exposure the excitations of the proximal and distal sides bring about neutralisation, the organ assuming a dia-phototropic position. If the intensity or duration of the stimulating light be further increased, it is easy to see that while excitation transmitted to the distal side is being increased, the excitatory contraction on the proximal side may, at the same time, be decreased owing to fatigue brought on by over-stimulation. ”

“ The approach of an abscess to the surface of the body, by a law similar to that which determines the approach of a plant to the surface of the earth—the reparation of a fractured bone, by the creation and disposition of elements not then existing in the body—and many similar cases, warranted him in assuming that all these processes were exactly analogous to what we call disease, being disturbances of the animal economy accompanied by pain ”

“ It was the Work of Nature in this Case (and what she was endeavouring to perform) to disburden herself of those disproportionate and offensive Particles, which by their Continuance in the Body would but have occasioned an irregular Motion of the Fluids, and consequently a Discomposure of it’s whole Frame: For the animal Body being nothing else but a Congeries of Canals, filled with different Liquors, it must necessarily suffer very much, and it’s Actions be irregular, if any Heterogeneous Particles become incorporated therewith. ”

“ If the surgeon be ambidexter, it does not matter where he stands: but if he uses one hand more adroitly than the other, he should place himself on the right side when he wishes to operate on the left eye ”

“ For although an organ diseased in structure will, under some circumstances, as Abernethy long ago observed, yield its characteristic secretion, yet, unless we know the extent of the disease, which is just the thing we can almost never be certain about, excitement of it is never without danger. We should therefore excite the primary organ with more or less energy, with more or less caution, or not at all, according to circumstances. ”

“ Besides, I wish such persons to observe that the grand artery and the arterial vein are of much harder and firmer texture than the venous artery and the hollow vein; and that the two last expand before entering the heart, and there form, as it were, two pouches denominated the auricles of the heart, which are composed of a substance similar to that of the heart itself; and that there is always more warmth in the heart than in any other part of the body ”

“ Besides, in the body of a living animal laid open, we can with our eyes perceive the ventricles of the heart171 both charged and distended by the contraction of the auricles, and more or less increased in size according to the charge; and farther, we can see that the distension of the heart is rather a violent motion, the effect of an impulsion, and not performed by any kind of attraction. ”

“ It is further to be noted that if the habitual use of the right hand tends in any degree to stimulate the development of the left cerebral hemisphere, then the examples of strongly-marked cases of such must greatly exceed those of the reverse type; since the left-handed man is almost invariably ambidextrous, and so subjects both hemispheres to the frequent stimulus of efferent nerve-force. ”

“ It is a settled principle of physiology, that nothing can stimulate or morbidly excite the body, without setting on fire the animal propensities. Tight-lacing does certainly do this. And as Amitiveness is located at the lowest part of the base of the brain, tight-­lacing, in rendering the brain and nervous system morbidly active, thereby necessarily kindles impure feelings. ”

“ The varieties of these sensations depend, firstly, on the diversity of the nerves themselves, and, secondly, of the movements that are made in each nerve. We have not, however, as many different senses as there are nerves. We can distinguish but seven principal classes of nerves, of which two belong to the internal, and the other five to the external senses. The nerves which extend to the stomach, the oesophagus, the fauces, and the other internal parts that are subservient to our natural wants, constitute one of our internal senses. ”