The two lobes must be separated, and the above-mentioned experiment made with each distinctly, and any difference in the results remarked; if one lobe float, and the other sink, it should be noticed whether it is the right or left that floats. Each lobe is then to be cut into several pieces, taking care not to confuse those of the right with those of the left.”
Having examined the physiological principles upon which the hydrostatic test is established, and explained the manner in which it is to be conducted, it remains for us to enumerate the several objections which have been urged against its validity.
1. A fœtus may breathe as soon as its head is without the vagina, and immediately die.—This is one of the great arguments adduced by Dr. Hunter;[[77]] “a child,” says he, “will very commonly breathe as soon as its mouth is born, or protruded from the mother, and in that case may lose its life before its body be born; especially when there happens to be a considerable interval of time between what we may call the birth of the child’s head, and the protrusion of its body. And, if this may happen when the best assistance is at hand, it is still more likely to happen where there is none; that is, where the woman is delivered by herself;” and he adds, “if a child makes but one gasp, and instantly dies, the lungs will swim in water as readily as if it had breathed longer, and had then been strangled.” This opinion, however, must not be received without qualification. We admit that under such circumstances a portion of the lungs will become inflated, and therefore swim in water; but it would appear from the more precise and comprehensive views of later physiologists, that respiration is not completely performed on the first effort, but that it is a process gradually advancing to perfection; and that it will be more or less protracted according to the degree of vigour of which the infant is possessed. Portal has shewn by experiments[[78]] that the air enters the right lung sooner than the left, and that the left lobe is very often not at all dilated for several days. The same fact was observed by Blancardi.[[79]] Dr. Hutchinson states that he was informed by a late physician to the Foundling-hospital at Naples, who opened daily, on an average, the bodies of ten or twelve infants, which had generally died within twenty-four hours after birth, that he hardly ever found more than a very small portion of the lungs dilated by air; this portion was frequently not larger than a walnut in its green shell, and but rarely larger than a hen’s egg, and it was commonly situate in the right lung.[[80]] “I have seen,” continues the author above cited, “a case where the right lobe, when separated from the left, sank in water, though this was the most dilated by respiration, and the infant had lived forty hours, and cried pretty strongly: but it died from suffocation by being overlaid, as it is popularly termed, by the mother, which had produced such an engorgement of blood in the lungs, as to counterbalance the influence which the small quantity of air they contained could have exerted on their specific gravity. A piece somewhat more than a cubic inch in volume was the greatest portion that in this case floated in water.”
2. The lungs may have been artificially inflated.—It is so generally known, observes Dr. Hunter, that a child born apparently dead may be brought to life by inflating its lungs, that the mother herself, or some other person, might have tried the experiment. It might even have been done with a most diabolical intention of bringing about the condemnation of the mother. There exists not a doubt but that such an operation would impart buoyancy to the lungs, although the fact has been doubted. Camper, Jager, Schmitt, and Buttner decided the question by numerous experiments.
3. The lungs may float, in consequence of putrefaction.—We have stated on a former occasion that the buoyancy of the human body is materially influenced by the putrefactive process, (vol. ii, p. 40.) Haller procured the lungs of a child that died before its birth. They were of a dark red colour, and both when entire, and when cut in pieces, sank in water. A portion being left to putrefy in water, the colour became brighter, it was covered with air bubbles, ascended gradually as the process of putrefaction advanced, and at length reached the surface, where it continued to float. But in answer to the objection which such a fact would seem to oppose to the validity of the hydrostatic test, let it be remembered that the lungs are particularly unsusceptible of the putrefactive process, and resist it longer than any of the soft parts. So that the body must be very far advanced in decomposition before the lungs are found to participate in it. Camper instituted a number of experiments upon infants, at Amsterdam, by exposing their bodies to the action of water, as well as to that of air, and his results fully confirm the fact we have just stated. Ballard was called upon to examine a child, the muscles of whose face were reduced to “boulli”—were in a state of solution—and in which putrefaction had advanced so far as even to prevent discrimination of the sex, notwithstanding which the lungs immediately sunk. If we make incisions into these organs, when in a state of advanced putrefaction, we shall observe air bubbles of a considerable size, and running in lines along the fissures, between the component lobuli of the lungs; where such phenomena present themselves we may be assured, says Dr. Hunter, that the air is emphysematous, and not that which has been introduced by respiration; for, in this latter case, the air bubbles will be hardly visible to the naked eye. But there still remains another mode by which we may determine whether the gas diffused in the texture of the pulmonary organs be the effect of respiration, or decomposition. It consists in pressing portions of the lungs between the fingers, or twisting them in a folded cloth, with all the force we can command; when, should the gas have arisen from putrefaction, the portions thus treated will sink in water; a change which no force, however powerful, will effect in those cases where the gaseous distention has arisen from respiration.
From the view which we have taken of the hydrostatic test, and of the objections which have been urged against its validity, the practitioner will be enabled to appreciate its importance. Plouquet, desirous of procuring additional evidence, respecting the existence of respiration, from the condition of the pulmonary organs, proposed a test founded on the absolute weight of the lungs compared with that of the body. Respiration produces two important changes in them—by inflating their texture it diminishes their specific gravity; and by promoting a determination of blood to their vessels, it increases their absolute weight; upon the former of these changes, the hydrostatic test is founded, as we have already explained; on the latter, Professor Plouquet endeavoured to found his “Nova Docimasia Pulmonaris,” which is now very generally known by the name of Plouquet’s test, or assay. The blood-vessels, observes this distinguished physiologist, being collapsed and compressed in the lungs of the fœtus, admit only a small portion of blood; but after respiration, being dilated, and extended, and more free in the expanded lungs, they receive a greater quantity; in consequence of which they become still farther expanded, and of greater calibre. As this increased capacity of the vessels is necessarily permanent, a greater quantity of blood will remain after death in the arteries and veins, and more especially in the latter, than in the lungs of those infants who have never respired, and consequently the absolute weight of the lungs must be increased.
In conformity with these views, Plouquet found on examination, that the body of a male infant, born dead, and which had not respired, weighed 53040 grains, the lungs inclusive; and that these latter organs alone weighed 792 grains; the proportion of the lungs to the body, in weight, was therefore in this case as 1 to 67. In another infant, under similar circumstances, he found the proportion as 1 to 70. On examining an infant, born at the full period, and which had respired, the proportion was found to be as 2 to 70, so that the weight of the lungs was absolutely doubled by the act of respiration.
It would be a loss of time to enumerate the different objections which have been urged against the validity of this test, on various grounds, many of which admit of an easy answer. It is sufficient to state that experiments, subsequent to those of Plouquet, by Haartman,[[81]] Struve,[[82]] Schmitt, and Lecieux,[[83]] have shewn that no constant relation between the weight of the lungs and that of the body, under the circumstances above mentioned, can be established. The reason of which, as Dr. Hutchinson has justly observed, without considering the influence of variation in the original construction of the body, is sufficiently accounted for, by the great diversity in the manner in which respiration is established in new-born infants. We have already stated that, in a great proportion of them, it is but gradually and slowly effected; and that several days even may elapse before the lungs are fully dilated. Dr. Gordon Smith[[84]] is disposed to believe that data might be obtained for a just conclusion upon this point, if practitioners would institute farther inquiry into the subject; and, with this impression, he has been induced to enter more fully into the history of the test, than we deem necessary, believing as we do, that it can never afford evidence sufficiently decisive for practical application. Daniel has proposed a modification of Plouquet’s test, but which is more objectionable even than that which he professes to improve. The same physiologist considers that an inference may be drawn from the increased circumference of the thorax, and the vaulted appearance it assumes after respiration. The objections urged by Dr. Hutchinson to these latter indications appear to us to be unanswerable; the circumference of the thorax, says he, varies so much in infants of the same age and sex, both absolutely and in proportion to other parts of their body, that it cannot be possible to obtain any decisive evidence from it. The vaulted appearance of the chest is almost equally fallacious in the generality of cases, or else it is devoid of utility; because the figure of the thoracic parietes is not much changed until respiration has been fully established, and then we have other and more certain means of detecting its existence. Besides which, it appears from the experiments of Schmitt, that the thoracic parietes were distended outwards by artificial insufflation after death, as much as they are by actual respiration as it occurs in the new-born infant. With these remarks we shall dismiss the subject of Docimasia Pulmonaris, and proceed to inquire whether the structure of the heart is capable of affording any useful indications. There can be no doubt but that, some time after birth, we shall find on inspecting the heart, evident marks of the altered course of the circulation. The foramen ovale will be closed, and in extending our examination, we shall find that the ductus arteriosus and canalis venosus, have collapsed and assumed the appearance of imperforated ligaments; but it must be remembered that such changes require some time for their completion, and in cases where the child has perished shortly after its birth, we do not believe that the alteration in structure will be sufficiently obvious to afford any information of practical application. The degree of importance which is to be attached to the arched state of the diaphragm has been already appreciated. The empty state of the urinary bladder and intestines has been alluded to by some authors, as affording a degree of presumptive evidence, since the evacuation of the urine from the former, and that of the meconium from the latter, are performed by most living children soon after birth. We are, however, inclined to attach but very little importance to such indications; and with regard to the meconium, every practitioner in midwifery knows well that it is frequently evacuated by the pressure of the maternal parts on the child during its passage through the pelvis; especially in breech presentations.
The stomach and intestines ought, in every case, to be considered as important objects of examination. It is possible that the trace of some aliment may be discovered, if so, no further proof can be required as to the child having lived. If any thing more than simple mucous fluid exist in the stomach, it should be examined by chemical tests. This remark, which we owe to Dr. Hutchinson, applies especially to the possibility of poison having been exhibited; and on this point the mucous membrane of the stomach will furnish useful evidence. If there should appear any fluid in this viscus, resembling water, it will be necessary to examine its nature, and to ascertain if any vegetable matters be present in it, such as portions of weeds, straw, &c. In our examination we should always keep in mind the possibility of the child having been destroyed by drowning, strangulation, poisoning, and the infliction of wounds, subjects which we have already so fully discussed in the second volume of our work, that we do not consider it necessary to dwell upon them in this place.
The cranial cavity.—For the examination of this part Dr. Hutchinson has given us some very minute and valuable instructions, of which we shall avail ourselves. The cranial cavity, he observes, should be exposed, by making, in the first instance, an incision through the integuments of the skull, penetrating to the bone, from the root of the nose to the spinous process of the second or third cervical vertebra; another incision of the same kind should extend from one ear to the other, passing transversely over the summit of the head. Each of the four triangular portions of integuments thus formed, should then be detached from the cranium, beginning at their apex and terminating at their base. The temporal and occipital muscles should then be separated in a similar manner. After examining the state of the cranium, the bones may be removed by dividing the membranous connection between the parietal, frontal, temporal, and occipital bones, with scissars. This, however, should be done without lesion of the vessels of the brain, or of the venous sinuses; in order to avoid the lateral sinus which always contains fluid blood, and which is situated very near the mastoidean angle of the parietal bone, Dr. Hutchinson directs the anatomist, when the point just indicated is approached, to deviate a little from the membrane, and to cut the parietal bone itself near its margin. In the first place, the view of the brain will afford presumptive evidence of its age; previous to the termination of the sixth month it will appear as a soft mass, equally white throughout its whole extent; in the eighth month the cerebral substance will have acquired more consistence, its interior will present a reddish colour, although its surface still remains white. The pia mater, which in the earlier stages seemed only to be over its surface, will now be found adherent to it; and some of those grooves and undulations become apparent, which afterwards constitute the circumvolutions. In pursuing the dissection of the brain, the practitioner must be careful in noting every morbid appearance, such as congestions, extravasations, &c., for the cause of death may have arisen from the injured structure of these parts.