ration.

Of Respi- nel, heated from 95° to 106°. Fishes live very well at 72°; and Lucas, in his history of mineral waters, speaks of carp that were living in a hot bath, whose temperature was at least equal to that of the human body. How this equable temperature is preserved, cannot be completely explained. We know that the heat of the human body is commonly moderated by perspiration; but in some cases, as in that of Dr Fordyce alluded to above, where the heated atmosphere was filled with watery vapour, this could have little effect. We can ascribe it only to the action of the living principle.

248 Voice.

voice.

It was long ago observed by Aristotle, that those animals only who possess lungs, have a true voice, and this opinion is confirmed by the experience of modern naturalists. We find, that only mammalia, cetacea, birds, reptiles and serpents, can utter vocal sounds. Several tribes below these do indeed emit certain sounds, especially insects; but these are owing to vibrations of the air in consequence of the agitation of their external organs. It is only in mammalia and birds that the voice becomes an interesting object of enquiry; for that of the cetacea is little more than blowing and grunting, and that of the other two classes is either hissing or croaking. 249 Amazing Nothing can exceed, in variety and execution, the variety of human voice; as will readily be allowed, if we consider the human the complicated structure of the human vocal organs, and the almost infinite variety of changes of which they are susceptible. Dr Barclay has calculated these with great accuracy, proceeding on the principle, that where a number of moveable parts constitutes an organ destined to some particular function, and where this function is varied and modified by every change in the relative situation of the moveable parts, the number of changes produceable on the organ must at least equal the number of muscles employed, together with all the combinations into which they can enter. Now, the muscles proper to the five cartilages of the larynx, are at least seven pairs; and fourteen muscles that can act separately or in pairs, in combination with the whole, or with any two or more of the rest, are capable of producing 16,383 different movements; not reckoning as changes the various degrees of force and velocity, nor the infinitely varied order of succession by which they may occasionally be brought into action. The number appears almost incredible; but to lessen the surprise, it must be recollected that we speak not here of the powers possessed by any individual, which will depend on habits and circumstances, but on the powers of the vocal organs, considered in the abstract, free from all the influence of custom, equally indifferent, and equally disposed to act in any order of succession, in any combination, and with any degree of force and velocity of which their original powers were susceptible.

If the powers we have mentioned appear astonishing, and able to account for many thousands of these varieties observed among the voices of the human species, we have further to add, that the muscles alluded to are only the proper muscles of the larynx, or the muscles restricted in their attachments to its five cartilages. These are but a few of the muscles of voice. In speaking we use a great many more. Fifteen pairs of different muscles, attached to the cartilages, or os hyoides, and acting as agents, antagonists, or directors, are constantly employed in preserving the cartilages of the larynx steady, in regulating

the place of their situation, or moving them as occasion of Respirequires, upwards and downwards, backwards and for- ration. wards, and in every way, directly and obliquely, according to the course of the muscular fibres, or in the diagonal between different forces. These muscles, independent of the former, are susceptible of 1,073,741,823, different combinations; and co-operating with the seven pairs of the larynx, of 17,592,186,044,415, exclusive of the changes which must arise from the different degrees of force and velocity, and the infinitely varied order of succession in which they may be brought into action.

But these are not all that co-operate with the larynx, either in forming or changing the voice; the diaphragm, the abdominal muscles, the intercostals, and all that directly or indirectly act on the air, or on the parts to which the chondral and hyoidal muscles are attached, contribute their share. The os hyoides could not be raised unless the inferior jaw-bone were previously fixed by the temporals, masseters, and internal pterygoids; and a similar assistance is likewise furnished by several other auxiliary muscles that fix the head, sternum, and scapula; to these we must add some pairs belonging to the pharynx and isthmus faucium, and some also belonging to the tongue, which, combining with others, give to that organ an inconceivable variety of movement; and so quickly, that, in rapid utterance, they change its state 3000+ Barclay's times in a minute. Thus Haller could articulate 1500

Anat. Nomen.

letters in a minute, which required 1500 contractions, P. 70. and as many relaxations of the lingual muscles t.

250

The principal organ of voice is the larynx, which is Mechanism proved by the circumstance that, when this is injured, of voice the voice is either lost, or rendered very indistinct. In and speech ordinary respiration the chink of the glottis seems to be in a relaxed state, and when this chink is contracted, voice is produced, and the sound of the voice is more or less shrill, according as the glottis is more or less contracted. By this contraction of the glottis alone we can produce only inarticulate sounds, varied indeed almost infinitely with respect to intensity and tone, by the action of the muscles. The production of speech requires the action of the tongue, the lips, the palate, and the teeth; and the articulations are most complete, when all these parts are most perfect in their structure, and in the most healthy condition. Too great length or shortness of the tongue, swelling of this organ in consequence of inflammation, &c. imperfection of the palate, loss of the teeth, swelling of the lips, all serve to render speech imperfect and inarticulate. The strength of the voice depends on the quantity of air expired, and on the contraction of the glottis; and consequently those animals who have the most capacious and most dilatable lungs, together with an ample cartilaginous and elastic larynx, will, other things being equal, have the strongest voice.

251

Among the various effects of the human voice, there Ventrilois none more calculated to produce surprise in the hear- quism. ers, than that extraordinary talent which some men possess of deceiving their hearers into a belief, that the sounds which they utter do not proceed from the real speaker, but from situations at a distance. This talent has been termed ventriloquism, from an idea that the voice of the speaker proceeded not from the mouth, but from the belly. The most remarkable instance of this rare talent of which we have heard, is that of M. FitzJames, who was formerly at Paris, and exhibited in London in the year 1803. Mr Nicholson has given an

amusing,

Of Respira- mouth of a ventriloquist are uttered in such a direction tion. that the hearers may receive the impression of some echo with much more force than they can receive the * Manches-original sounds *. It may be doubted whether such ter Meechoes can take place in an ordinary room filled with a moirs, vol. large assembly; and on the whole we are inclined to x. part ii. consider this phenomenon as being effected partly by the v. 622. gradual emission and a skilful management of a large quantity of air taken in by a full inspiration, and partly by the influence which the performer is capable of exerting over the imagination of his hearers.

253 Voice of brutes.

Several of the mammalia have a characteristic voice, which is formed by particular organs. These are in some animals tense membranes; in others peculiar cavities opening into the larynx, and sometimes appearing like continuations of the laryngeal ventricles. Thus the neighing of the horse is effected by a delicate, and nearly falciform, membrane, which is attached by its middle to the thyroid cartilage, and has its extremities running along the outer margins of the opening of the glottis. The braying of the ass is produced by means of a similar membrane, under which there is an excavation in the thyroid cartilage. In this animal there are also two large membranous sacs opening into the larynx. The purring of the cat seems to be owing to two delicate membranes that lie below the ligaments of the glottis. Some of the monkey tribe, especially the simia seniculus and beelzebul, have the middle and fore +Blumen- part of the os hyoides formed into a spherical bony cavity, by which these animals are enabled to produce those bach's Comp. horrible and penetrating tones, which can be heard at Anat. chap. vast distances, and have gained them the name of howling apes +. See MAMMALIA, N° 33.

XV.

254 Voice of birds.

255

Relations

of respiraother func

tion with

tions.

lation.

The simplest vocal organ seems to be that of birds. These animals have, on the sides of the windpipe next the lungs, and at the opening of the bronchiæ, two membranous folds which partly close the pulmonary aperture of the windpipe, and the aperture next the head is susceptible of great contraction and dilatation. In short, the vocal organ of birds may be considered as one of the most perfect wind instruments, very much resembling, both in its structure and effect, a clarinet or hautboy, the opening next the lungs being similar to the reed of these instruments. For some remarks on the song of birds, see ORNITHOLOGY, N° 42; and for farther observations on the voice, see ANATOMY, Part I. N° 122.

In tracing the relations of respiration with the preceding functions, we must deviate a little from our usual order, and begin with those between respiration and circulation, as it seems to be through the medium of the circulating system that respiration principally acts on the other functions. The relations between respiration and circulation are the most immediate and the most obvi256 With circu-ous. When the breathing is most free and rapid, the circulation is most vigorous and active; while in laborions or interrupted respiration, the action of the heart and arteries becomes slow, feeble, irregular; and where the lungs are deprived of oxygenous gas, the arteries gradually cease to pulsate, and soon after the motion of the heart ceases. If the stimulus of oxygen be not too long withheld, so that the lungs can again be excited to action, first the heart, and then the arteries, gradually renew the exercise of their functions, and the circulation proceeds as before. On the application of these princiVOL. XVI. Part II.

tion.

257

ples depends the recovery of those apparently dead from Of Respira asphyxia (suffocation, drowning, &c.) When the circulation becomes languid from indolence, from depressing passions or the want of accustomed stimuli, we feel about the breast a peculiar sensation, which physicians call anxiety, and which is relieved by a deep inspiration; by sighing, yawning, &c. Violent exertions of the respiratory organs, such as laughing, coughing, singing, talking unusually long or loudly, quicken the circulation, sometimes to an alarming degree, so as to occasion hæmorrhage in such as are predisposed to that affection. Breathing in an atmosphere that is much rarefied, as on the top of a high mountain, has often the effect of producing plethora and hæmorrhage; though this, perhaps, is imputable rather to a want of the ordinary pressure on the surface of the body. When the circulation through the lungs is impeded With sensaor obstructed, a determination of blood takes place to tion. other parts, especially to the head. The effects produced on the brain and other organs of sensation, by the breathing of impure air, are dreadful. When the same quantity of air is repeatedly respired, there is experienced, first, great anxiety about the breast, and this soon becomes intolerable; the face swells, becomes livid, or even black, and feels excessively hot; sparks of fire seem to dance before the eyes; the sight becomes depraved; giddiness, ringing in the ears, and confusion of thought succeed; and if fresh air be not soon supplied, the subject of the experiment loses both sensation and motion, and falls into a state resembling apoplexy +.+ Kite's When rarefied air is breathed, the nervous system expe- Essay on riences a kind of excitement; agreeable sensations are Apparent produced with a disposition to mirth and cheerfulness; but if the person continue for some time in such a situation, an unusual languor, heaviness, and disposition to sleep, come on ‡. We need not here describe the plea- + Saussure surable sensations excited by the respiration of nitrous Voyagedans oxide, as these have been already related under CHEMI- les Alpes, STRY, N° 366. The exhilarating effects which a pure P. 559. and serene atmosphere produce on the general system, and the uneasy sensations experienced under a thick and clouded sky, are partly referable to this head. The nervous system also acts on the organs of respiration. In some affections of the brain, respiration is much quickened, while in others, especially the comatose affections, it is slow, laborious, and often attended with that peculiar noise called stertor. It is well known what effect anxiety, eagerness, hope, or desire, have on the respiration. According as one or other of these passions is predominant, the breathing becomes hurried, irregular, or suspended.

Death,

p. 25.

t

258 An evident relation takes place between respiration With moand motion. The breathing is quickened by exercise; tion; and when there is a considerable debility of the muscular system, the slightest exertion produces hurried respiration, panting, &c. In those animals that possess the greatest powers of motion, respiration is most free, and the air most extensively diffused over the body. In birds, not only the lungs are very extensive, but the air is conveyed into the bones of the skull, and into the hollows of the larger cylindrical bones; and in insects which have the most rapid motions, the air penetrates to every part of the body. Motion, as well as sensation, becomes unusually free and vigorous in rarefied air, and during the respiration of nitrous oxide; while in cases + 38

of

259 With digestion.

*See Bichat Re

The organs and functions of respiration sympathise with those of digestion. When the former function is most free, the latter is generally most healthy; the respiration of pure or rarefied air, or of the nitrous oxide, is attended with an increase of appetite, and of the digestive powers, as was experienced by M. Saussure while wandering among the Alps, and by Davy while respiring the gas of Paradise. Again, when digestion is impaired, or when the stomach is overloaded, the breathing is rendered difficult, laborious or irregular, and in many cases of affection of the stomach, cough is a very common symptom. These effects produced on the respiratory organs in consequence of impaired digestion, are ascribable chiefly to the pressure on the diaphragm by the distended stomach.

Many other relations might be pointed out between respiration and the other functions of the animal economy, but our limits do not permit us to enlarge further on the subject *.

For an account of the morbid affections of respiracherches tion, such as sneezing, hiccup, coughing, anxiety, dysla Vie et la pnæa, or difficulty of breathing, see the article MEDI

Physial. sur

Mort.

260 Nature of

CINE.

CHAP. IX. Of Nutrition and Assimilation.

THE function by which the nutritious particles renutrition. ceived by a living being are assimilated to the nature of that being, or become part of its substance, is properly called nutrition. This is the completion of the process which, in most animals, is the combined result of several other operations. Thus, in the superior animals, from man to the mollusca, the whole process of nutrition consists of digestion, absorption, circulation, and respiration; by the two last of which the nourishment received is changed into perfect blood, and fitted for the support and renewal of the several parts of the system. From the account of the constituent parts of the blood given under CHEMISTRY, N° 2660, it will appear, that this fluid contains within itself the principles of which every part of the body is composed. Thus it contains fibrine, which is the chief principle of the muscular parts; phosphate of lime, which forms the basis of the bones; albumen and gelatine, the chief constituents of cartilages, ligaments and tendons, &c. These principles are conveyed by the arterial blood, during its circulation, to those parts of the system where they are required, for renewing waste, or supplying deficiencies, and thus they are assimilated to the nature of the body.

261

Each assi

The power of assimilation, so remarkable in living milating or- bodies, is not the same in every assimilating organ; gan produ- but each has the property of converting the materials it ees peculiar receives (provided they be susceptible of this conversion) changes. into a peculiar substance. Thus the stomach always converts the food into chyme; the intestines change it

into chyle; but if chyle, or what is very similar to it, of Nutrifresh milk, be received into the stomach, this organ tion and Aexerts on it the usual change, and does not pass it for- simitation. ward into the intestines unaltered, though we know by experiment, that fresh milk is capable of being taken up unchanged by the absorbents of the bowels*. A-* Fordyc gain, blood is always perfected within the circulating on Diges tion, p. 159. vessels; and if ahyle or fresh milk be injected into the arteries, it produces dangerous cffects, while the fresh blood of another living animal may be transfused into these vessels without injury. In like manner, if a piece of fresh muscular flesh be cut from a living animal, and applied to the muscles of another living animal, also newly divided, the two parts unite, and are immediately assimilated; and even fresh bone may, in the same manner be ingrafted on the living bones of the same, or of a different species of animalt; while substances + Phil. that are foreign to the nature of the animal body, when Mag. vi. introduced into the blood-vessels, prove fatal, and when 308. inserted into a wounded muscular or bony part, prevent the wound from healing.

262

These circumstances show that assimilation is a che- Assimilamical process, though modified and regulated by the tion a cheaction of the living principle. The chemical nature of mical proassimilation is most distinctly proved by the well-known cess. experiment of colouring the bones of an animal, by feeding it on madder. The particles of the madder, which we know to have a strong affinity for phosphate of lime, are carried unchanged from the stomach into the blood-vessels, and are thence conveyed, probably in combination with the phosphate of lime there contained, into the substance of the bones, where they are deposited, and remain for a considerable time.

are the

nerves.

263 We have considered nutrition as performed by the Nutrition circulating vessels. It has been supposed that the nerves not per of nutrition; but this strange hypothesis formed by organs is completely overturned by an experiment of the second Monro, which proves that the limb of a frog may be preserved alive and nourished by the blood-vessels, after its communication with the brain has been cut off by dividing the nerves.

264

and zoo

In insects and zoophytes, where there are no circula- Nutrition ting vessels, nutrition must be a very simple operation. in insects According to Cuvier, it is performed by imbibition; the pores of the animal's body receiving immediately the nutritious fluids on which it feeds.

very

phytes.

265

limited.

In plants and animals, the assimilating power has al- Assimilatways certain limits prescribed to it; its influence is ing power generally confined to the sort of food congenial to the species, and its strength is varied according to circumstances, as the age, the habits, and the state of health. Those which are young assimilate faster than those which are old; and one species, which may partly be owing to the nature of their food, will assimilate much faster than another. Certain worms that feed on animal and vegetable substances will, in twenty-four hours after their escape from the egg, become not only double their former size, but will weigh, according to Redi, from 155 to 210 times more than before. Most oils are of very difficult assimilation; and those which are volatile will often resist the long-continued and the varied action of the living organs; will mingle with the parts, and, undecomposed, communicate their flavour.

Other circumstances respecting nutrition have been

noticed

Of noticed in the first part of ANATOMY, No 130; and Secretion. the chemical doctrine of assimilation is more fully considered under CHEMISTRY, N° 2567-2571.

265 Secretion.

267

Organs.

268 Kinds of

CHAP. X. Of Secretion.

THAT function by which any organ, or set of organs, separates from the general mass of blood certain principles intended to perform some important office in the animal economy is called secretion; and the substances so separated, are called secretions.

The secretory organs in the more perfect animals are very numerous, and some of them very complex. The most simple of them seem to be the cellular texture, and the mucous membranes. The next in simplicity are the conglobate glands, and perhaps the spleen, while the more complex organs are the liver, the testicles, the atrabiliary capsules, &c. An account of all these organs, as they occur in the human body, has been given in the first part of the article ANATOMY; and the corresponding organs of the inferior animals, with others not found in man, are described by writers on comparative anatomy, especially Cuvier and Blumenbach.

Secretion appears to be of three kinds: 1. Transudasecretion. tion, in which the secreted matters merely ooze through the pores of the secreting organ. This takes place in the lowest classes of animals, as in zoophytes, insects, and some worms, but rarely in the human subject. 2. Exhalation, in which the secreted fluids are poured out into cavities by certain branches of the arteries with open mouths, called exhalants. This appears to take place in many organs of the most perfect animals, especially from the mucous membranes, the synovial glands, &c. 3. Secretion, properly so called, in which the blood passes through glandular bodies, where a part of it is decomposed, and carried out in another form by particular tubes called excretory ducts. This is the case with most of the secreting organs, as the salivary glands, the lachrymal glands, the liver, the pancreas, the testicles, and a few others.

269

Secreted matters.

270 General

The secreted fluids are chiefly the following: lymph, serum, tears, mucus, saliva, pancreatic juice, gastric juice, enteric juice, bile, semen, synovia, fat, marrow, cerumen or ear-war, and in the female, milk. The other matters secreted, which may rather be termed solid than fluid, are albumen, gelatine, fibrine, and phosphate of lime. On the nature and properties of all these substances, see the article CHEMISTRY, Chap. xix. sect. 3.

With respect to the secretions in general, we may remark, that they are considerably influenced by age, sex, various affections of the mind, and various bodily diseases. They are formed by organs which are sometimes modifica capable of supplying the deficiencies of each other; tions of se- they are subjected to the influence of the atmosphere, and to the temperaments of the body; they are sometimes mixed together, and by this combination their nature is changed.

cretion.

Of

while it at the same time separates and distinguishes every organ. From its elasticity, and the lubricating Secretion. fluid which it holds within its cells, it facilitates motion, and thus assists the action of all the muscular parts and organs. That it is susceptible of great dilatation is proved by the phenomena of anasarcous dropsy; and the gradual evacuation of the water when anasarcous limbs' are punctured, as well as the passage of extraneous bodies below the skin from one part to another, seem to show that it possesses considerable contractile powers. It is chiefly, however, as a secreting organ that we are here to consider the cellular membrane; and in this way its function is of the utmost importance. The fatty matter, that is so copious in most of the superior animals, is contained within particular cells or bags of the cellular membrane, and is found in greatest quantities below the skin, especially on the sternal part of the belly, and about the kidneys. In some animals, as the hog, the seal, the walrus and the cetaceous tribes, it forms a layer several inches in thickness, and in all the water animals above mentioned it is nearly fluid. these animals it not only serves the purposes of a warm covering by the slowness with which it conducts heat; but, by diminishing their specific gravity, renders their motions on the surface of the water much more easy and expeditious. One of the most important uses of the fat seems to be to supply nourishment to the body, when the ordinary channel is obstructed, or the system rendered incapable, from torpor or disease, of receiving food. When fat persons are attacked by fever, or similar acute diseases, they become emaciated, sometimes to so great a degree, as to appear a mere skeleton; and those animals who sleep during winter, though very fat when they retire to their dormitories, are extremely lank and lean when they quit these on the return of spring. In all these cases the fat alone is absorbed, and supplies the waste that takes place in the body, and would otherwise prove fatal.

Το

On the actions of the cellular membrane, see Bichat, Anatomie Generale, tom. i.

272

Some physiologists have supposed that the bile secret-Action of ed by the liver is not formed entirely from the blood of the liver. the vena portarum, but partly from the hepatic artery. Dr Saunders who has examined the arguments in favour of this supposition, decides against it, and considers the usual opinion of the bile being solely secreted from the blood of the vena portarum, as quite satisfactory. It has also been supposed, that the whole of the bile is not secreted by the liver, but that the gall bladder has a share in this office, and is not merely a reservoir, like the urinary bladder. This supposition is highly improbable, although we think there can be little doubt that the bile undergoes, within the gall bladder, some peculiar changes, which render it better fitted for the func tions it has to perform. We know that the gall bladder is very muscular, and that there is an appearance of follicles within it. It is therefore probable that some matter is secreted from its internal surface, which produces a necessary change in the bile.

273

The principal use of the bile seems to be to stimulate Uses of the the intestines, and thus keep up their energy and peri-bile. staltic motion, though it is probable that, besides this office, it performs several others of importance in the animal economy, such as assisting in the decomposition of the food, and thus forming chyle; and acting as a 382 general