Page images
PDF
EPUB

operate, are in some respects different from those of ordinary Touch is very easily shown. Thus, the feeling of tickling is excited most readily in parts which have the least tactual sensibility, the armpits, flanks, and soles of the feet, whilst in the points of the fingers it cannot be excited." The fact also that the susceptibility of the surface to temperature does not correspond to the acuteness of touch is pointed out, and in connexion with this point we would remark, that certain anomalous instances of local loss of sensation, would almost induce us to infer that the power, if not the nervous fibrils themselves, by which we judge of variations of temperature, is altogether distinct from the perception of mere contact. A case confirmatory of this view was related to us by an intelligent practitioner, of a patient who, although he had lost the sensation of touch in the skin of one of the lower extremities, so that he was not conscious of contact, still retained in the affected part the perception of heat and cold.

The sense of taste, according to the author, ought to be considered as a peculiar modification of that of touch, but in this position we do not agree. The common experience of mankind might, we think, be adduced to show that these two faculties are essentially distinct in kind. The difference in the ultimate texture of nerves having undoubtedly separate offices, is not so marked as to enable us to pronounce upon the functions of a part simply upon the grounds of anatomy; and, consequently, the fact of a part of the fifth pair supplying the organ of taste, for we regard, notwithstanding the experiments of Panizza, the lingual to be the true nerve of taste, is not sufficient to disprove the existence of special fibres being allotted to that sense.

The sections on the senses of Vision and Hearing are written in a philosophic spirit, and are worthy of careful consideration, but some space having been devoted to these subjects in a former review, we can only here quote the following passage illustrative of the complex character of what, in the absence of such evidence, might be regarded as simple ideas.

"The sense of Vision depends, in the first place, on the transference to our minds of the picture which is formed upon the retina; this picture puts us in possession of the outlines, lights and shades, colours and relative positions, of the objects before us: and all the ideas respecting the real forms, distances, &c. of bodies, which we found upon these data, must be considered in the light of perceptions either instinctive or acquired. Many of these are derived through the combination, in our minds, of the visual sensations, with those derived from the sense of touch. Thus, to take a most simple illustration, the idea of smoothness is one essentially tactile; and yet it constantly occurs to us, on looking at a surface which reflects light in a particular manner. But, if it were not for the association, which experience leads us to form, of the connection between polish as seen by the eye, and smoothness as felt by the touch, we should not be able to determine, as we now can do, the existence of both these qualities, from an impression communicated to us through either sense singly." P. 277.

In treating of the muscular system, the author has availed himself of the excellent researches of Mr. Bowman; but we regret that, in such a treatise, no reference is made to the important researches of Matteucci, upon muscular contractility.

The second division of the work comprehends the organic functions to which, in the present edition, considerable additions have been made.

In the history of the digestive process the celebrated and well-known investigations of Dr. Beaumont are throughout adopted. The observations of Mr. Goodsir on the structure and action of the intestinal villi, are thus recorded and adopted.

"From the recent observations of Mr. Goodsir, it appears that the villi are enclosed in a very delicate membrane (analogous to that which lies under the epidermis and epithelium in the skin and mucous membrane); and that, when digestion is not going on, they are covered by an epithelium. The space between the reticulations of the blood-vessels and lymphatics, towards the extremity of each villus, is occupied, whilst the absorption of chyle is taking place, by a number of spherical vesicles or cells, varying in diameter from the 1-1000th to 1-2000th of an inch, and containing an opalescent fluid. At the part where the vesicles approach the granular texture of the substance of the villus, minute granular or oily particles are seen. When the intestine contains no more chyme, the vesicles disappear almost entirely, the lacteals empty themselves, and the villi become flaccid; the epithelium, which had fallen off during the process of Absorption, is then renewed. The vesicles at the extremities of the villi can scarcely be regarded in any other light than as cells, whose lives have but a very brief duration,-selecting from the materials in contact with the surface of the villi, and appropriating these to their own growth,-then liberating them, by solution or disruption of the cell-wall, in a situation where they can be absorbed by the lacteals." P. 395.

In connexion with cutaneous absorption, some interesting examples are quoted from different writers, showing the great activity and importance of the process. Dr. S. Smith mentions that a man who had lost nearly three pounds by perspiration during an hour and a quarter's labour in a very hot atmosphere, regained eight ounces by immersion in a warm bath for half an hour. Dr. Dill relates the case of a diabetic patient who, for five weeks, passed 24 lbs. of urine every twenty-four hours, his ingesta during the same period amounting to 22 lbs. ; and as he had lost in weight only 27 lbs. when he died, there must have been an absorption of 43 lbs. from the atmosphere during the time.

In treating of the respiratory organs the author truly observes that "in regard to the intimate structure of the lungs of Man and of the Mammalia it is difficult to speak with confidence."

The account of Reisseissen, according to which the air-cells are merely the globular dilatations of the ultimate ramifications of the bronchial tubes, is certainly erroneous: nor is the opinion of Mr. Addison much more satisfactory, that the air-cells do not exist prior to birth, but that they are produced by the parietes of the minute bronchial tubes becoming dilated into little pouches, in consequence of the pressure exerted by the atmospheric air admitted into the lungs in respiration.

An excellent paper upon this subject, containing the results of a careful examination of the pulmonary texture, made by Mr. Rainey, of St, Thomas's Hospital, has been lately read before the Medico-Chirurgical Society; and as these investigations, in addition to affording clear and satisfactory evidence upon many points which are at present a matter of dispute and uncertainty, contain some novel facts, a brief allusion to them will not be misplaced.

The principal results are as follows:

1. A bronchus, when traced from its commencement to its termination,

is seen to be in the first part of its course more or less cartilaginous; it then becomes destitute of cartilage, retaining however a perfectly circular form, and having no air-cells opening into it; farther on, being still circular, numerous air-cells open into it; lastly, the air-cells increase so much in number, and open into the bronchus so closely to one another, that the tube can no longer retain its circular form, but becomes reduced to an irregular passage, running between the cells, and ultimately reaching the surface of the lobule, ends by forming a terminal air-cell.

2. The air-cells are small irregularly-shaped cavities, having generally four or five unequal sides; those which are situated close to the small bronchial passages open into them by well-defined circular apertures, whilst those which are situated at a distance from these passages open one into the other, an arrangement which those who are acquainted with the disposition of the air-cells in the injected lung of the frog and serpent will readily comprehend; in fact, each lobule of the lung of the mammal and man, with its bronchial passages and appended cells, may in some sort be regarded as a repetition of the whole lung of the frog.

3. The border of each air-cell is surrounded, in addition to the epithe lium, by a number of fibres definitely arranged in a circular manner, so as to form a circumscribed limit to each cell. The fibres appear to be elastic, and have no resemblance whatever to muscular fibres, striped or unstriped.

4. The sides or walls of the air-cells consist of a dense plexus of capil laries, situated, in the interior of the lobules, between two layers of the pulmonary membrane; but on their exterior between this membrane and the pleura in the case of the lobules on the outer surface of the lung, or between it and the interlobular areolar tissue in those lobules which bound the interlobular spaces. There is thus, between every two cells only one vascular network, so that the small stream of blood in each capillary vessel is acted on by the air upon both sides, whilst in the frog, serpent, &c. there being two plexuses of vessels between two cells, the blood in the capillaries is only aerated on one side.

5. The number of capillary plexuses is not the same as that of the aircells, one net-work passing between and supplying several cells; or, in other words, one terminal branch of the pulmonary artery supplies the plexuses of several air-cells.

6. An important part of these investigations relates to the anatomy of the foetal lungs, prior to the act of respiration; these, when well injected, are distinctly seen to possess air-cells, fully formed and surrounded, as in the animal which has respired, by plexuses of blood-vessels.

As we trust that the whole of this valuable paper will be speedily pub. lished, we do not notice the interesting observations of Mr. Rainey upon the seat and effects of tubercle.

Dr. Carpenter alludes to the researches of M. Bourgery upon the force of the respiratory muscles, and the capacity of the lungs at different periods of life and in the two sexes. According to these inquiries the development of the air-cells continues up to the age of 30, at which time the capacity of respiration is the greatest; it subsequently decreases, especially in persons who suffer from cough, the violence of such expiratory effort frequently causes rupture of the air-cells, and thus gradually pro

duces that emphysematous state of the lungs, which is so common in elderly persons. The power of increasing the volume of air by a forced inspiration is much greater in young than in old persons, and is twice as great in males than in females of the same age, a circumstance which is evidently connected with the extent to which muscular efforts can be carried in these classes respectively.

Since the work before us was written, a valuable contribution to the physiology of the respiratory muscles and the capacity of the lungs, has been made by Mr. Hutchinson, in a paper read before the Statistical Society, and subsequently published in their Journal, for September, 1844. The deductions of this gentleman rest upon an extended basis, and the results being tabulated and accompanied with illustrative diagrams, are readily comprehended.

By the term "capacity" Mr. Hutchinson "signifies that quantity of air which an individual can force out of his chest by the greatest voluntary expiration, after the greatest voluntary inspiration." The experiments respecting" capacity," were made with the assistance of an instrument called the spirometer, or "breath-meter," and those on the force of the muscles by a mercurial guage.

[ocr errors]

It has long been known that the quantity of air capable of being admitted into the lungs varies in different individuals, and these researches have established this in a remarkable degree, showing the modifying effects of stature and occupation, and of health and disease. Thus, the mean 'capacity" of 172 males under the height of 5 feet 8 inches is 220 cubic inches, whilst that of 82 males of from 5 feet 11 inches to 6 feet, is 255 cubic inches. It is clearly a desirable thing to discover the cause of such a marked difference, and Mr. Hutchinson asserts that he has "discovered a relation intimately existing between this capacity and power and the height of the individual," and further on, states it to be a rule that "for every inch of height (from 5 to 6 feet) eight additional cubic inches of air at 60° are given out by a forced expiration." The exceptions to this rule among healthy persons, occur among very stout and corpulent individuals, whose capacity stands the lowest. This, if confirmed, is a very interesting generalization, and strongly supports, both by the rule and its exception, the chemical theory of animal temperature; for it thus appears that the activity of the heating apparatus, the lungs, is definitively proportioned to the bulk of the body to be warmed, except in the case of fat persons, in whom a thick layer of adipose matter, which is a bad conductor of heat, exists on the surface of the body.

Another curious and unexpected result is, that the force of the expiratory muscles is about one-third stronger than that of the inspiratory; thus whilst a person of 5 feet 6 inches elevates the mercury 3.87 inches by the power of his expiration, he only raises it 2.70 inches by his inspiration. This difference depends probably more upon the favourable leverage of the abdominal muscles on the fore part of the trunk, and the erectores spinæ behind, than upon the actual size of those muscles when contrasted with the diaphragm, pectorales, serrati, and the other muscles of the inspiratory class.

The effects of employment, diet, and disease are strikingly shown; for example, in the early stage of phthisis the healthy "capacity" being

204 cubic inches, the capacity of the diseased lungs was in some cases 135 cubic inches; and in the advanced stage, as would be anticipated from the evidence of morbid anatomy, the difference becomes much greater, so that the "capacity" of a person which in health would be 229 cubic inches, was reduced to 80 cubic inches. Mr. Hutchinson conceives that his tests afford an additional and important means of detecting the existence and extent of pulmonary disease; and even of discovering other affections, such as hernia and perforation of the membrana tympani, seated in organs indirectly related to the respiratory apparatus.

The chapter on Nutrition having been, as the author states, almost entirely re-written, contains the most recent inquiries upon the subject. The admirable researches of Dr. Prout, since confirmed and extended by the German school, have shown that all the azotised parts of the animal body are derived from one peculiar proximate principle, called by Prout albumen, and by Mulder protein; if to this we add fatty matter, certain salts, and water, we have all the materials required for the nutrition of animals. In illustration of his views, Dr. Prout has selected milk as an example, observing that "milk is designed and prepared by nature expressly as food, and it is the only material throughout the range of organization that is so prepared. In milk, therefore, we should expect to find a model of what an alimentary substance ought to be—a kind of prototype, as it were, of nutritious matter in general."

We have ourselves, however, always considered the ovum as a case more in point, on account of its containing only one protein compound, albumen, and this is the instance adduced by Dr. Carpenter. From the albuminous matter of the egg of the fowl all the various and complex organs are derived, the first and most essential part of the process consisting in the conversion of that substance into fibrin, which is to be regarded as the plastic or organizable constituent of the body. "To use a rather homely illustration, albumen, fibrin and organized tissue, stand much in the same relation to each other, with raw cotton, spun yarn, and the woven fabric." Now the conversion here alluded to, is, we must presume, effected by the agency of those important organic instruments called nucleated cells, of the powers of which the author has given a full account in the several divisions of his work relating to the nutritive actions.

There is no discovery of modern times which has worked such mighty changes in established opinions, as that connected with the cell theory, which, originating in the researches of Schleiden into the ultimate texture of vegetables, was extended in the celebrated work of Schwann (Mikroskopische Untersuchungen, &c.) to the organization of animal structures. By these investigations, it has been ascertained, that with some few exceptional cases, every part of every animal and plant is, in the first epoch of its formation, developed from a nucleated cell; that by the inherent and independent powers of this cell and by the metamorphoses it experiences all the organic tissues are formed; and, more than all, that every act of the process of nutrition-secretion-absorption-assimilation -growth, and decay, instead of being, as until this theory they were in all the higher animals invariably considered to be, immediately dependent upon the blood-vessels and absorbents, are in reality accomplished by parts which are essentially extra-vascular. Although the facts here announced

« PreviousContinue »