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that the life of the foetus is indirectly but largely dependent upon the condition of the mother. But the maternal influence has been conceived to extend much beyond this; and it has been affirmed, that the excited imagination of the mother may occasion an alteration in the form of particular parts of the foetus, so as to give rise to nævi and to all kinds of mothers' marks, as they have been termed.
These may consist of spots resembling raspberries, grapes, &c.; or there may be deficient formation of particular parts, and some of the cases, that have been adduced in favour of their having been induced by impressions, made upon the mother during pregnancy, are sufficiently striking. There are numerous difficulties, however, in the way of accepting the cause assigned. If a child be born with nævi of any kind, the recollection of the mother is racked to discover, whether some event did not befal her during gestation to which the appearance can be referred, and it is not often difficult to discover some plausible means of explanation.
Cases have occurred in which the mother, when a few months advanced in pregnancy, has been shocked by the sight of a person who had lost his hand, and the child has been born devoid of a hand. A young female, a few months gone with child, visited a brother in one of the hospitals of London who was wounded in the side. His condition affected her extremely. Her child was born with a deep pit precisely in the same part that was wounded in the brother.
These are samples of the thousands of cases, that have been recorded, or that have occurred to different individuals. Similar instances have even been related of the inferior animals. In the extracts from the minute book of the Linnean Society of London, an account is given, by Mr. George Milne, F. L. S., of the effect of the imagination of a female cat on her young. One afternoon, whilst Mr. Milne and his family were at tea, a young female cat, which had arrived at the middle of gestation, was lying on the hearth. A servant, by accident, trod very heavily on her tail; she screamed violently, and, from the noise emitted, it was evident, that a considerable degree of terror was mingled with the feeling from the injury. From so common a circumstance no extraordinary result was expected; but, at the full time, she dropped five kittens, one of which was perfect, but the other four had the tail remarkably distorted; and all distorted in the same manner.
Are we to consider these and similar cases of mal-formation or monstrosities to be dependent upon the influence of the maternal imagination upon the fœtus in utero; or are we to regard them as coincidences, the cause being inappreciable, but such as we find to give occasion to vicious organization, where no coincidence with excited imagination can be discovered? Under the head of generation we have combated the notion, that the mother's fancy can have any effect during a fecundating copulation. Let us see, then, what we have to admit in a case where
a female is, we will suppose, four months advanced in pregnancy, when she is shocked at the appearance of one who has lost his arm, and the child is born with the like defect. It has been seen, that the communication between the mother and the fœtus is of the most indirect character, and that no endeavours have succeeded in throwing substances from one side of the placenta to the other; that the circulation of the fœtus is totally distinct from that of the mother; and that she can only influence the fœtus through the nutritive material she furnishes—whatever be its character—and consequently that such influence must be exerted upon the whole of the fœtus and not upon any particular part. Yet, in the supposititious case we have taken, the arm must have been already formed, and the influence of the mother's fancy must have been exclusively exerted upon its absorbents, so as to cause them to take up again that which had been already deposited!
The case we have assumed is not environed with more difficulty than any of the kind. It is a fair specimen of the whole. Yet how impracticable for us to believe, that the effect can be in any way connected with the assigned cause; and how much more easy to presume, that the coincidence, in such cases, is accidental. Cases of hare-lip are perpetually occurring, yet we never have the maternal imagination invoked; because, it is by no means easy to discover any similitude between the affection and extraneous objects. Moreover, in animals of all kinds—even in the most inferior, as well as in plants—monstrous formations are incessantly happening where maternal imagination is out of the question.
As a cause of monstrosities, therefore, the influence of the maternal imagination has been generally regarded as an inadmissible hypothesis. By many it has been esteemed ridiculous; yet it manifestly receives favour with Sir Everard Home, and is perhaps hardly worthy of the strong epithets of condemnation that have been applied to it, although sufficiently incredible. The third hypothesis, with regard to defective germs, we have already canvassed under generation, and attempted to prove it insufficient.
The second, consequently, alone remains, and is almost universally adopted. Independently of all disturbing influences from the mother, the foetus is known to be frequently attacked with spontaneous diseases, such as dropsy, ulceration, gangrene, cutaneous eruptions, &c. Some of these affections occasionally destroy it before birth. At other times, it is born with them; and hence they are termed connate or congenital.
Where a part has been wanting, the nerve or blood-vessel or both, proceeding to it have likewise been found wanting; so that the defect of the organ has been thus explained; without our being able, however, to understand the cause of the deficiency of such nerve or blood-vessel.
In some of the cases of monstrosities confusion of two germs seems to have occurred. Two vesicles have been fecundated,
and subsequently commingled, so that children have been produced with two heads and one trunk, or with two trunks and one head, &c. &c.
The animal temperature of the foetus cannot be rigidly determined. The common belief is, that it is some degrees lower than that of the mother; and it is affirmed, that the temperature of the dead foetus is higher than that of the living. The foetus must, therefore, possess the means of refrigeration. Edwards found, in his experiments, that the temperature of young animals is inferior to that of the adult; which is in accordance with the general belief regarding that of the foetus in utero. In some cases, as in those of the kitten, puppy and rabbit, if they be removed from the mother and exposed to a temperature of between 50° and 70°; their temperature will sink,—as happens to the cold-blooded animal,—to nearly the same degree. The faculty of producing heat he found to be at its minimum at birth; but it progressively increased, until in about fifteen days the animal acquired the power in the same degree with the adult. This was not the case, however, with all the mammalia. It seemed to be confined to those animals that are born blind; in which a state of imperfection probably existed in other functions. It was the same with birds as with the mammalia; birds, hatched in a defective state, as regards their organs generally, have the power of producing heat defective; whilst others, born in a more perfect condition, have the organs of calorification more capable of exercising their due functions. The opinions with regard to the temperature of the human infant vary. Haller asserts, that it has less power of producing heat than the adult, and such is the opinion of Despretz, Edwards, and the generality of physiologists. The latter gentleman estimates it at 94.25° of Fahrenheit. On the other hand Dr. John Davy affirms, that the temperature of young animals generally, and that of a newly-born child, which he particularly examined, was higher than in the adult. It is impossible to account for this discordance; but the general results of experiments will be found to agree with those of Edwards. The foetus certainly possesses the power of forming or separating its own caloric; otherwise its temperature should correspond with that of the mother, which, we have seen, is not the fact.
That the secretions are actively exercised in the fœtus is proved by the circumstance, that all the surfaces are lubricated nearly as they are subsequently. The follicular secretion is abundant, and at times envelopes the body with a layer of sebaceous matter of considerable thickness. Vauquelin and Buniva have asserted, that this is a deposit from the albumen of the liquor amnii; but in reply to this it may be urged that we do not find it except on the body of the foetus. It is not on the placenta or umbilical cord, and is most abundant on those parts of the foetus, where the follicles are most numerous. The fat also exists in quantity after the fifth
month. The greatest question has been with regard to the existence, in the fœtal state, of some of the secretions which are of an excrementitious character. For example, by some, the urinary secretion is supposed to be in activity from the earliest period of uterine existence, and its product to be discharged into the liquor amnii. Such is the opinion of Meckel, but it does not rest on any basis of observation. The only circumstances, that in any manner favour it, are the fact of the existence of the kidneys at a very early period; and that at the full time, the bladder contains urine, which is evacuated soon after birth. On analysis, this is found to be less charged with urea and phosphoric salts than in after life.
Of the meconium we have already spoken. It is manifestly an excretory substance, produced, probably, by the digestion of the fluids of the alimentary canal. Vauquelin analyzed the meconium evacuated after birth, and found it composed of water, about twothirds; of a substance of a vegetable nature, but sui generis, about onethird; mucus, a few hundredth parts, and a little bile. It appears, consequently, to be less azoted than the excrement of the adult.
Lastly, the cutaneous perspiration is supposed to be a fœtal excretion, and to be poured into the liquor amnii; but although this is probable, we have no positive evidence on the subject.
III. Functions of Reproduction.—These require no consideration. They are inactive during the foetal state, except that the testicles and the mammæ appear respectively to secrete a fluid, which is neither sperm nor milk, and is found in the vesiculæ seminales in the one case, and in the lactiferous ducts in the other.
OF THE AGES.
Under this head we have to include the modifications that occur in the functions during the life of man, from birth until dissolution. The different ages may be separated as follows:—Infancy, comprising the period from birth till the second dentition;—childhood, that between the second dentition and puberty;—adolescence, that between puberty and manhood;—virility, that between youth and old age; and old age.
Sect. I. Infancy.
The age of infancy extends from birth to the second dentition, or until about the seventh or eighth year. By Hallé, and after him by Renauldin, Rullier, Adelon, and others, this has been again subdivided into three periods, which are somewhat distinct from each other, and may therefore be adopted with advantage. The one comprises the period between birth and the first dentition, generally about seven months; a second embraces the whole period of the first dentition, or up to about two years; and the third includes the whole interval, that separates the first from the second dentition.
1. First period of Infancy. As soon as the child is ushered into the world, it assumes an independent existence, and a series of changes occurs in its functions of the most sudden and surprising character. Respiration becomes established, after the manner in which it is to be effected during the remainder of existence; and the whole of the peculiarities of foetal circulation cease,—the organs of these peculiarities being modified in the manner to be described presently.
As soon as the child is extruded it begins to breathe, and at the same time to cry. What are the agencies, then, by which this first inspiration is effected, and this disagreeable impression is made upon the new being at the moment when it makes its appearance amongst us? This has been an interesting topic of inquiry amongst physiologists. A few of the hypotheses, that have been indulged, will be sufficient to exhibit the direction which the investigation has taken.
Whytt,—whose views were long popular, and still have supporters, conceived, that before birth the blood of the foetus is properly prepared by the mother; and that when, after birth, it no longer receives the necessary supply, an uneasy sensation is experienced in the chest, which may be looked upon as the appetite for breathing, in the same manner as hunger and thirst are ap