John Gray McKendrick

“ VOICE (Fr. voix, from Lat. vox) , the sound produced by the vibrations of the vocal cords, two ligaments or bands of fibrous elastic tissue situated in the larynx. It is to be distinguished from speech, which is the production of articulate sounds intended to express ideas. Many of the lower animals have voice, but none has the power of speech in the sense in which man possesses that faculty. There may be speech without voice, as in whispering, whilst in singing a scale of musical tones we have voice without speech. ”

“ TOUCH may be defined as a sense of pressure, referred usually to the surface of the body. It is often understood as a sensation of contact as distinguished from pressure, but it is evident that, however gentle be the contact, a certain amount of pressure always exists between the sensitive surface and the body touched. Mere contact in such circumstances is gentle pressure; a greater amount of force causes a feeling of resistance or of pressure referred to the skin; a still greater amount causes a feeling of muscular resistance, as when a weight is supported on the palm of the hand ”

“ The coincidence of the time of sleep with the occurrence of the great terrestrial phenomena that cause night is more apparent than real. The oscillations of vital activity are not correlated to the terrestrial revolutions as effect and cause, but the occurrence of sleep, in the majority of cases, on the advent of night is largely the result of habit. Whilst the darkness and stillness of night are favourable to sleep, the state of physiological repose is determined more by the condition of the body itself. Fatigue will normally cause sleep at any time of the twenty-four hours. ”

“ Here you see at once one of the serious disadvantages at which the physiologist is placed in the prosecution of his science. The things the natural philosopher deals with are dead things. He can isolate them and interrogate them at pleasure by experiment, submitting them to all sorts of conditions and changes of circumstances, without the risk of destroying them or even of altering the property he wishes to examine. Many of the phenomena he has to investigate are of a tolerably permanent character, and the things he operates upon are, as a rule, not the seat of constant change. ”

“ If the sensation of cold were due to the irritation of a specific-nerve fibre, the sensation of cold would be referred to the tips of the fingers. When any part of the skin is above its normal mean temperature, warmth is felt ; in the opposite case, cold. The normal mean temperature of a given area varies according to the distribution of hot blood in it and to the activity of nutritive changes occurring in it. When the skin is brought into contact with a good conductor of heat there is a sensation of cold. A sensation of heat is experienced when heat is carried to the skin in any way. ”

“ The pitch of the note of a musical instrument, however, depends on the pitch of the first or fundamental tone, while the partials are added with greater or less intensity so as to give a special character to the sound; and in the case of a vowel tone the pitch does not appear to depend on that of the fundamental tone but on the pitch of the resonance cavity, as adjusted for the sounding of any particular vowel. When we wish to pronounce or sing a vowel the oral cavity must be adjusted to a certain form, and it is only when it has that form that the vowel can be sounded. ”

“ The insane frequently have subjective tastes, which are real to the patient, and frequently cause much distress. In such cases, the sensation is excited by changes in the taste-centres of the brain. Increase in the sense of taste is called hypergeusia, diminution of it hypogeusia, and its entire loss ageusia. Rare cases occur where there is a subjective taste not associated with insanity nor with the circulation of any known sweetish matters in the blood, possibly caused by irritation of the gustatory nerves or by changes in the nerve centres. ”

“ We are familiar with motion every day of our lives. We know, first of all, of great movements of matter, such as the wheeling of the planets in their elliptical orbits round the sun, the spinning of the earth on its axis, or the still grander movements of the firmament, as revealed by the proper motions of the stars. Such movements impress the imagination with a sense of vastness and of irresistible power. Then there are the movements on the surface of the world itself—the tides, the flow of rivers, the hurricane, the clouds travelling athwart the sky, and many others. ”

“ A body having a uniformly level surface, like a billiard ball, is smooth ; a body having points irregular in size and number in a given area is rough ; and if the points are very close together it gives rise to a sensation, like that of the pile of velvet, almost intolerable to some indivi duals. Again, if the pressure is so uniform as not to be felt, as when the body is immersed in water (paradoxical as this may seem, it is the case that the sensation of contact is felt only at the limit of the fluid) , we experience the sensation of being in contact with a fluid. ”

“ All the phenomena of sleep point to a diminished excitability of the cerebral nerve-centres and of the spinal cord. Contrary to what is often stated, there can be no doubt that reflex action is in partial abeyance and that the spinal cord is in a state of partial inactivity as well as the brain. The only nerve-centres that do not sleep are those absolutely essential to life, such as those connected with the heart, with respiratory movements, and with the distribution of blood by the vaso-motor arrangements ”

“ This is another example of how valuable to humanity the frog has been in the way of giving scientific information. It is not too much to say that each time your physician sees you when you are ill he brings to the study of your case knowledge that has been gathered for him by the physiologist from the frog. As we are in the habit of commemorating by monuments the services of those who have been benefactors to humanity, I know no animal,—no tiger, lion, or panther,—that better deserves a bronze statue than the humble frog. ”

“ It depends on the fact that many waves of sound that reach the ear are compound wave systems, built up of constituent waves, each of which is capable of exciting a sensation of a simple tone if it be singled out and reinforced by a resonator (see Sound) , and which may sometimes be heard without a resonator, after special practice and tuition. Thus it appears that the ear must have some arrangement by which it resolves every wave system, however complex, into simple pendular vibrations. When we listen to a sound of any quality we recognize that it is of a certain pitch. ”

“ By an organ physiologists mean a part of the body devoted to a special use or purpose, or, as we say, a function. A muscle has its own work to do, in a sense as true as that the heart has its own work to do in acting as a force-pump to drive on the blood through the blood-vessels, or, in other words, to keep up the circulation. It is important to notice that a muscle may be regarded as an independent living thing, an organ that in certain conditions might live and work by itself. ”

“ Our arrangements for studying muscle are not yet complete. We have already seen that a muscular contraction is so rapid as to make it impossible to follow all its phases with the unaided eye. The questions at once occur to us: how long a time does it take to contract? if it does not contract at the same rate throughout its contraction, for how long a time does it contract quickly, and for how long a time does it contract more slowly? ”

“ This shows that when the little machine cannot give its output of energy at the expense of carbo-hydrate or of fat, it sacrifices a part of its own framework. The muscle engineer, when he finds himself short of the ordinary fuel, seizes hold of combustible portions of his own engine, as if he were determined at all costs to do the work required of him. This is only a somewhat fanciful analogy, but it gives us an insight into what probably occurs in a muscle.
An engineer is desirous, chiefly for the sake of economy, to get as much effective work as possible out of the engine he constructs. ”

“ Science, then, demands the accurate measurement of time, and no small fraction of time is too insignificant to be of importance. The twentieth, the hundredth, the thousandth of a second is to science as precious as an hour may be to many people. It may be said without irreverence that to science a day is as a thousand years, and a thousand years as one day. The methods of science for this purpose are founded on two sets of appliances: first, the use of instruments, like a tuning-fork, that are found to vibrate or move at a known rate, say one hundred or five hundred times per second ”

“ But the constituents in the food stuffs are not quite the same as those in muscle, and they are therefore subjected to many chemical processes in digestion by which they are first converted into stuffs that exist in the blood. From these stuffs in the blood the muscle builds up its- substance. Now all of these stuffs, from the scientific point of view, contain energy in what is spoken of as a potential state, that is to say, it is resting, ready to be set free, ready to do work, and when it is set free it may become, as it does become in the case of the muscle, mechanical energy and heat. ”

“ In the body, the muscles are always partially on the stretch. They are never "on the slack," to use a familiar phrase, and they are ready to exert a pull on the bones to which they are attached, the instant they begin to contract. Thus no power is wasted. Further, as has been ingeniously shown by Professor Marey, the elasticity breaks the force of the shock produced by the sudden contraction of the muscle, and the energy of the contraction is expended more gradually and effectively than if the muscle had been non-elastic. ”

“ It is evident, therefore, that, considered as an engine, a muscle is not much better as a transformer of energy than the best steam-engine now constructed, while it is inferior to certain gas-engines which are said to return as much as twenty per cent in the form of effective mechanical energy. The muscle, however, has this great advantage over any engine, that the heat it produces supplies one of the conditions of its very existence, the maintenance of a certain uniform temperature. ”