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petites for meat and drink. To satisfy this appetite, the brain excites the expansion of the chest, to prevent the fatal effects that would ensue, if the lungs were not immediately aroused to action. This appetite is supposed to commence at birth, owing to the circulation being quickened by the struggles of the fœtus at that period, and to an additional quantity of blood passing through the lungs, which excites them to action, and seems to be the immediate cause of the appetite.
Haller ascribed the first inspiration to the habit which the fœtus has acquired, whilst in the uterus, of taking into the mouth a portion of the liquor amnii; and he supposed, that it still continues to open its mouth, after leaving the mother, in search of its accustomed food. The air, consequently, rushes into the lungs, expands them; the blood is distributed through them, and a regular supply of fresh air is needed to prevent the blood from stagnating in its passage from the right to the left side of the heart.
Dr. Wilson Philip regards the muscles of inspiration as entirely under the control of the will; and he thinks, that they are thrown into action by the uneasy sensation experienced by the new being, when separated from the mother, and having no longer the necessary changes produced upon the blood by her organs.
Adelon thinks it probable, that the series of developments, occurring during gestation, predispose to the establishment of respiration. According to him, the lungs gradually increase in size during the latter months; the branches of the pulmonary vessels become enlarged, and the ductus arteriosus less; so that the lungs are prepared for the new function they have to execute. In addition to these alterations, he conceives, that the process of accouchement predisposes to the change; that, by the contractions. of the uterus, the circulation of the blood must be necessarily modified in the placenta, and consequently in the fœtus,—for he is a believer in the doctrine, that the foetus receives blood from the mother by the placenta. Owing to this disturbance in the circulation, more blood is sent into the lungs; and, when the child is born, it is subjected to new and probably painful impressions. "For instance," he remarks, "the external air, by its coldness and weight, must cause a disagreeable impression on the skin of the infant, as well as on the origin of all the mucous membranes; and, perhaps, the organs of the senses being, at the same time, suddenly subjected to the contact of their proper irritants, receive painful impressions from them. These different impressions being transmitted to the brain, they are reflected into the different dependencies of the nervous system, and, consequently, into the nerves of the inspiratory muscles: these muscles, thus excited, enter into contraction, in the same manner as the heart is stimulated to renew its contractions, during syncope, by inspiring a stimulating vapour."
None of these views satisfactorily explain the true physiology VOL. II.
of the first inspiration; nor is it probable, that any can be devised, which has not its difficulties. That which has been embraced by Dr. Bostock and Sir Charles Bell appears to us to be liable to fewer objections than any we have seen; and to explain the process, so far as is perhaps practicable, on mechanical principles. The first respiratory act, according to them, seems to be purely mechanical, and to result from the change of position which the child undergoes at birth. From the mode in which it rests in utero, every thing is done that position could effect, to diminish the dimensions of the chest; and any change in this position must have the effect of liberating the lungs from a portion of the pressure which they sustain. The head cannot be raised from the breast, nor the knees removed from the abdomen, without straightening the spine, and the spine cannot be reduced to a straight line without elevating the ribs, and permitting the abdominal viscera to fall; but the ribs cannot rise, nor the diaphragm descend, without enlarging the chest; and as the chest enlarges, the lungs, which are the most elastic organs of the body, will expand their air-cells, hitherto collapsed by external pressure, and the external air will rush in.
The same cause is considered to account for the new circulatory movement. The blood, which, in the foetus, had passed through the foramen ovale and the ductus arteriosus without visiting the lungs, is solicited from its course by the expansion of the chest, which draws the blood through the pulmonary artery as forcibly as it does air through the windpipe. The blood, thus exposed to the air in the lungs, becomes arterialized, and from this moment the distinction between the arterial and venous blood is established. The circulation, through the vessels peculiar to the foetal condition, now ceases, even without any ligature being placed upon the umbilical cord.
The sudden and important changes supervening in this manner, guide us to the decision of an interesting medico-legal inquiry,— viz. whether, in a case of alleged infanticide, the child has respired or not;—in other words, whether it has been born alive or dead?
After respiration has been established, the lungs, from being dark-coloured and dense, become of a florid red hue; are light and spongy, and float on water; on cutting into them the escape of the air in the air-cells occasions a crepitus, and a bloody fluid exudes; there is closure, or an approach to closure, of the foramen ovale; the ductus arteriosus is empty, as well as the ductus venosus; and the absolute weight of the lungs may be doubled.
Respiration having been once thoroughly established, the individual enters upon the period of infancy, which has now to engage our attention.
The animal functions during this period undergo considerable development. The sense of tact is but little evinced, but it exists, as the child appears sensible to external cold. At first the touch
is not exerted under the influence of volition, but towards the termination of the period it begins to be active. The taste is almost always null at first. Adelon thinks, that it is probably exerted on the first day as regards the fluids, which the infant sucks and drinks. We have daily evidence, however, that at an early period of existence, the most nauseous substances, provided they are not irritating, will be swallowed indiscriminately, and without the slightest repugnance; but before the termination of the period we are now considering, the taste becomes inconveniently acute, so that the exhibition of nauseous substances, as of medicine, is a matter of more difficulty. The smell is probably more backward than any of the other senses; the development of its organ being more tardy, the nose being small, and the nasal sinuses not in existence. In the first few weeks, sight and hearing are imperfectly exerted, but subsequently they are in full activity. The internal sensations, being instinctive, exist; all those at least that are connected with the animal and nutritive functions. Hunger and thirst appear during the first day of existence; the desire of passing the urine and fæces is doubtless present, notwithstanding they appear to be discharged involuntarily; and the morbid sensation of pain is often experienced, especially in the intestinal canal, owing to flatus, acidity, &c. During the first part of the period the child exhibits no mental and moral manifestations; but, in the course of a few weeks, it begins to notice surrounding objects, especially such as are brilliant, and to distinguish between the faces to which it has been accustomed and those of strangers; awarding the smile of recognition or of satisfaction to the former, the look of gravity and doubt to the latter. Locomotion is, at this time, utterly impracticable, as well as the erect attitude. The muscular system of the child is not yet sufficiently developed, the spinous processes of the vertebræ are not formed, and it has not learned to keep the centre of gravity—or rather the vertical line—within the base of sustentation. The function of expression is at the early part of the period confined to the vagitus or squalling, which indicates the existence of uneasiness of some kind; but, before the termination of the period, it unites smiles and even laughter to the opposite expressions, and will attempt to utter sounds, which cannot yet be considered as any attempt at conventional language. Sleep is largely indulged. Soon after birth it is almost constant, except when the child is taking nutriment. Gradually the waking intervals are lengthened; but still much sleep is needed, owing to the frail condition of the nervous system, which is soon exhausted by exertion however feeble, and requires intermission.
After birth, the child has to subsist upon a different aliment from that with which it was supplied whilst in the maternal womb. Its digestion, therefore, undergoes modification. The nutriment is now the milk of the parent, or some analogous liquid, which is sucked in, in the manner described under the head of Digestion.
For this kind of prehension the mouth of the infant is well adapted. The tongue is very large, compared with the size of the body, and the want of teeth enables the lips to be extended forwards and to embrace the nipple more accurately and conveniently. The action of sucking is doubtless as instinctive as the appetite for nutriment, and equally incapable of explanation. The appetite appears to be almost incessant, partly owing to the rapidity of the growth demanding continual supplies of nutriment, and partly perhaps owing to a feeling of pleasure experienced in the act, which is generally the prelude to a recurrence of sleep broken in upon, apparently, for the mere purpose of supplying the wants of the system, or the artificial desire produced by frequent indulgence. Often we have the strongest reason for believing, that the great frequency of the calls of the appetite is occasioned by the habit, with many mothers, of putting the child constantly to the breast; whilst in hose children that have been trained, from the earliest period of existence, to receive the nutriment at fixed hours only, the desire will not recur until the lapse of the accustomed interval.
Digestion is, at this age, speedily accomplished; the evacuations being frequent,—two or three or more in the course of the day, -of a yellow colour, something like custard, or curdy, and having by no means the offensive smell, which they subsequently possess. During the first days after birth they are dark and adhesive, and consist of the meconium, already described. Young mothers are apt to be alarmed at this appearance, which is entirely physiological, and always exists. The respiration of the infant is more frequent than in the adult, nearly in the proportion of two to one, and it is chiefly accomplished by the muscles that raise the ribs, on account of the great size of some of the abdominal viscera, which do not permit the diaphragm to be readily depressed. The stethoscope exhibits the respiration to be also much more sonorous; so characteristic, indeed, is it in this respect, that it has been called "puerile," by way of distinction. It appears to indicate a greater degree of dilatation of the bronchial ramifications, and, consequently, a greater admission of air than occurs in after life. The circulation is more rapid; the pulsations at birth being nearly twice as numerous as in the adult. Nutrition is very active in the development of the different organs. Calorification becomes gradually more energetic from the time of birth. The recrementitial secretions, as well as the excrementitial, are as regularly formed as in the adult; but the products vary somewhat. The urine, for instance, is less charged with urea, and contains benzoic acid; the perspiration is acidulous, &c. &c.
Adelon asserts, that these excretions are frequently insufficient for the necessary depuration, and that nature, therefore, establishes others that are irregular and morbid, in the shape of cutaneous efflorescences, &c. These can scarcely be regarded as depurations, unless we consider all cutaneous eruptions, that are connected with
gastric or digestive irritation, to be thus induced, which is more than problematical; especially as most of them are neither pustular nor vesicular, and therefore, not accompanied by any sensible exudation.
2. Second period of infancy, or first dentition.—This period embraces the whole time of dentition, and is considered to include the age between seven months and two years. In it, the external senses are in great activity, and continually furnishing to the intellect the means for its development, connected with the universe. The internal sensations are likewise active. From these united causes, as well as from the improved cerebral organization, the intellect is more strengthened during this period than perhaps during any other. The senses are continually conveying information, and perception is, therefore, most active, as well as memory; whilst imagination and judgment are feeble and circumscribed. The faculty of imitation is strong, so that by hearing the spoken language, and appreciating its utility, the child endeavours to produce similar sounds with its own larynx, and gradually succeeds,the greater part of its first language consisting of imitations of sounds emitted by objects, which sounds are applied to designate the object itself, in the manner we have seen elsewhere. The affective faculties are likewise unfolded during this period, but generally those of the selfish cast are predominant, and require the most careful attention for their rectification. Even at this early time of life, the effect of a well-adapted education is striking, and spares the child from numerous inconveniences, to which unlicensed indulgence in its natural passions would inevitably expose it. The general feeling is, that the infant is not yet possessed of the necessary intelligence to pursue the course that is indicated; but it is surprising how soon it may be made to understand the wishes of its instructor, and with what facility it may be moulded, at this tender age, in almost any manner that may be desired. During this period, the child is capable of standing erect and of walking. Previous to this, these actions were impracticable, for the reasons already stated, as well as owing to the weight of the thoracic and abdominal viscera; to the spine having but one curvature, the convexity of which is backwards; to the smallness of the pelvis, and its inclination forwards, so that it scarcely supports the weight of the abdominal viscera; and to the smallness of the lower limbs and the feebleness of their muscles, which are insufficient to prevent the trunk from falling forward.
These imperfections are, however, gradually obviated, and the child commences to support itself on all-fours; a position assumed much more easily than the biped attitude, owing to the centre of gravity being situated low, and the base of sustentation being large. In this attitude he moves about for some time, or his locomotion is effected by pushing a chair before him, or by being steadied by his nurse. Gradually he passes from place to place on his feet, by laying hold of surrounding objects, and, in proportion as the