The morbid state of the coats of the ovum may likewise cause the so•called moire, which, according to their consistency, are divided into mace fring,os, carnosce, cruentce, and tendinosa.. Valentin* distinguishes in the san guineous mass of nada carnosa a net of vessels, from which the blood issues. It is the vas cular net of the chorion, in which the mass of blood has been collected, in consequence of too great a supply from the uterus. By these means the villi are distended and removed. The ovum being thus degenerated, occasions defective respiration and nutrition of the foetus, which in consequence soon dies. The ovum, however, may still continue to grow, and is finally expelled. In this manner these woke are frequently the cause of miscarriage.
Kerckring* inveighed in a spirited and in genious manner against the strange accounts which were formerly given of these mokr.
To the diseases of the placenta are referred enlargement (Kyll, Pierrard, Devilliers), con gestion and apoplexy (J. Clarke, Darigan), calcareous concretions (Hannover). For the aetiology of malformations, this pathological anatomy of the placenta is; however, very un productive. None of these can be explained by it, nor were any accompanied by these pla cental diseases; Nor does the nosology of the foetus afford us much more information, notwithstanding the monograph given by J. Gmessent It cannot, however, be denied, that some of its diseases may give rise to deformities ; for in stance, chronic inflammation of the brain to hydrops ventriculorum cerebri, and this again to Acrania.
Perhaps also, a I Rokitansky states, a morbid condition of the valves may be the cause of some congenital abnormities of the heart. Yet, notwithstanding all this, the diseases of the fcettis can only, in a very limited sense, be assigned as the cause of its malformation; and hence the opinion of Otto, who ascribes to this source a greit many malformations, ought to be rejected.
4. A fourth, and assuredly very general, cause of malformation, consists in impeded de velopement of the foetus by some remote and un known cause. It is matter of dispute whether this deforming cause operates on the fmtus in its totality, or whether it affects originally only one system, which spreads its deforming influence over all the others. This last idea was embraced by Tiedemann, who at first de duced all monstrosities from some defect of the vascular, and later from the nervous system. In opposition to this hypothesis, I suggest the following considerations.
a. It is opposed to anatomical evidence. The cyclopia, whose nature consists in a more or less simplified eye and a displaced or absent external nose, is attributed by Tiede mann to the original absence of olfactory nerves, producing the deformation of the nasal cavity, and the original fusion of the optic nerves, and of the thalami nervorum opticorum effecting the simplification of the eye. I have found, however, in cyclopes,
more than once, olfactory nerves, and have likewise seen that there was no constant con currence between the simplified form of the eye and of the optic nerve. A double optic nerve may be found with a single eye-ball (Eller, Henermann). With complete dupli cation of the internal parts of the eye, and even with two separate eyes, I found a single optic nerve, and likewise a double, though not complete, as well as a single eye-ball, notwithstanding the entire absence of the optic nerve. Similar facts are quoted by Haller and G. F. Wolff. Hare-lip with cleft palate is attributed by Tiedemann to the original absence of olfactory nerves. G. Vrohk found them, however, in children with hare-lip. The nerves of organs may exist, although the organs themselves may be ab sent (Seiler, W. Vrolik); and inversely, the nerves may be wanting, while the organs are present (C. G. Buttner). In anencephali the body is very massive, notwithstanding the imperfect condition of the nervous centres. In double monsters there is no definite corre spondence between the condition of the nerv ous system and the duplication of the body (W. Vrolik).* b. Embryogenesis teaches that the forma tion of the several parts of the body is not essentially the result of that of the nervous system, but that, on the contrary, each part is formed and developed independently. I refer to what I have already said, in 1836 (in my treatise on Cyclopia), and am happy to find J. Muller, Rathke, Bischoff, Burdach, and Stannius, with me on this subject.
What is now proved for the nervous system, may equally be applied to the system of blood vessels ; and hence I presume to conclude, that no malformation whatever proceeds from a central system, but is occasioned merely by impeded developement, the cause of which remains concealed. This impediment may he confined to one part, or may be extended over more. This extension may sometimes stand` either in causal connexion with an original malformation, as for instance the dis placing of the nose in cyclopes ; or may take place in an entirely independent manner. In the latter case, it is a complication of mal formation, which proves that it may extend itself to more than one region of the body, and to more than one apparatus. I have met with an instance of this, in which to acrania, cyclopia, and absence of the lower jaw, was added ectopia of the intestines. If the origin of the malformation is derived from impeded developement, the so-called monstra per defectum are the result, and from excessive formation arise the monstra per excessum.