Paper - A study of the causes underlying the origin of human monsters 6
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Mall FP. A study of the causes underlying the origin of human monsters. (1908) J Morphol. 19: 3-368.
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A Study Of The Causes Underlying The Origin Of Human Monsters
Monsters in which Tissues must have been Destroyed - Magnesium Monsters, Cyclopia and Club-foot
It has been repeately noted by experimental teratologists that, whenever the malformation of an embryo is slight, there is a general retardation of development of the whole body which is more marked in some portions of the embryo than in others. Thus it is stated that the tail of an embryo is atrophic, or even club—shaped, a condition which cannot be brought about without some destruction or rearrangement of its tissues.
In the human embryo there are all gradations of form between typical anencephaly, atrophic head and deformed head; in fact, pure types are rarely seen. These varieties can be brought together under the general heading of atrophic heads. The tissue change in them ranges from histolysis to dissociation or even to maceration. In a general way the following table gives the frequency of variations of pathological embryos and of monsters per 100,000 pregnancies. The ﬁgures from which the table has been constructed will be found on pages 26, 27, 65 and 66, and may be considered to be fairly reliable:
Ptegnancies. Births. Normal Embryos Pathological Monsters.
and Foetuses. Embryos. 100,000 8 1,000 I2,ooo 7,000 61 5 Hydrocephalus . . . . . . . . . . . . . . . . . . . . . . . II9
Deformed head . . . . . . . . . . . . . . . . . . 953 . . . .
Anencephaly . . . . . . . . . . . . . . . . . . . . 574 I I9
Spina biﬁda . . . . . . . . . . . . . . . . . . . . 410 47
Face deformed . . . . . . . . . . . . . . . . . . 697 96
Deformed eye . . . . . . . . . . . . . . . . . . . I23 25
Deformed extremities . . . . . . . . . . . . 697 I I 5
The ﬁgures given under monsters are actual ﬁgures, those for hydrocephalus, etc., being from Panum, in which the total number is 618. This is practically equal to the 615 which I have obtained from various authors. My data, which are from 163 pathological ova, were multiplied by them up to the total estimated number of pathological ova per 100,000 pregnancies. “Deformed heads” I have paralleled with “hydrocephalus,” but I do not mean to infer that one is directly related to the other. Otherwise the subdivisions coincide. It is remarkable that in each instance there are about six of a given variety of embryonic monsters for each at full term. At any rate, the constancy of the ratios speaks volumes in favor of the genetic relation of monsters to pathological embryos.
In my collection there are ﬁve specimens of exomphalos (Nos. 115, I62, I66, 244 and 364), mostly in very young stages, in which there is an extreme degree of atrophy of the embryo. It is a question whether any of these embryos in which the atrophy is so extreme could possibly have lived much longer, for in them the body of the embryo is nearly destroyed.
In many of the specimens there is a marked distention of the central nervous system, and it would probably be more to the point if they had been classed with hydrocephalic monsters. The frequency with which hydrocephalus and dilatation of the embryonic nervous system are encountered makes it questionable whether anything is to be gained by the comparison.
As Giacomini has pointed out, the amnion is sometimes partly destroyed or is wanting entirely. More often, however, there is hydramnios, as is also the case with monsters. The excessive secretion of ﬂuids into the cavities of the body and into the amnion is often accounted for by a supposed interference with the circulation, and this theory is supported by removing the heart in young tadpoles (Knower’s experiment), which is always followed by general dropsy.
To come back to the deformed heads, in which there is not only an arrest of development, but also an actual destruction of many of the tissues, the head is more or less necrotic or stubby, often the brain is exposed, either in front or over the mid-brain, or the whole brain may be wanting. In some cases the lumen of the brain communicates directly with the exterior of the body, the edges of the opening often being rounded, that is, there has been an attempt to repair the wound. In other instances the whole brain has been destroyed and the medulla is markedly dilated and ﬁlls the whole of the stumpy head. In such specimens the face is more or less deformed and may be adherent to the thorax below without an intervening neck. So, with destruction of tissue, there is a slow and continued growth, for if there were not the chin and thorax could not have united.
There are all kinds of deformities of the face, from a simple atrophy, in which the external features are obliterated, to atrophic jaws, deformed or closed mouth, hare-lip, absence of the neck, or ears, which are not developed, are deformed. pointed or displaced. Such changes could not take place without a marked destruction of tissue and an attempt at further growth, which is necessarily irregular. Probably the most pronounced of all deformities of the face are those associated with the eyes, and my collection contains one specimen without eyes (No. 285), one with the eyes deep in the head (No. 135), and one with cyclopia (No. 201). The last belongs to the wonders among monsters, which has interested the thinking world for centuries.
In cyclopia the eye is in the middle of the face, is often partly double, the nose is above the eye, and the cerebrum is atrophic and usually single. Teratologists are in the habit of holding the single brain as primarily responsible for the condition, and I think they are right. We have seen repeatedly that the central nervous system suffers very frequently in pathological embryos, and a slight atrophy or destruction of the front of the brain in an early stage (like No. 12) might easily end in cyclopia. We cannot admit, however, that the tendency to produce cyclopia exists in the ovum, nor that a close-ﬁtting amnion did the mischief, as there is no evidence for these theories, and the facts are against them. If, however, the brain is malformed and the lack of correlation of growth of the parts does not push the frontal process down rapidly enough, the eyes move towards each other and unite. All this has been proved experimentally.
Ten years ago Born,‘ in making numerous experiments upon frogs’ eggs, occasionally produced cyclopia by splitting the head through its sagittal plane after the medullary plate is formed and then readjusting the halves. They united at once, but in a few instances a double eye was formed. Later Spemannz made similar experiments, and he also produced cyclops embryos. In some of Spemann’s experiments Triton eggs were ligated in the sagittal plane during segmentation, and frequently embryos resulted with double heads, one or both being cyclops. He believed that this experiment proved that the anlage for the cyclops eye was defective from the beginning and is not produced by concrescence of two anlages. Levy“ also produced cyclops embryos by cutting off the front of the head of Triton larvae. In the course of two weeks the two eyes approached each other and formed a double eye, but they were not fused; the pigment layer became destroyed, or at least was absent at these points. The two optic cups touched each other.
A year ago Harrison produced a new variety of cyclopia by removing the entire brain from frogs’ embryos. The eyes moved to the back of the head in these specimens and appeared to unite into a single vesicle in the region usually occupied by the pineal eye. By pricking the extreme anterior end of the embryonic shield in Fundulus eggs Lewis found, in 1905, that many of the eggs developed into cyclops embryos. All stages of eyes were formed, from a double eye, and hour-glass eyes with two lenses, to oblong eyes with either two lenses or a single lens. The optic cups blended absolutely, thus proving the mode of development in these eyes. Lewis also found that in many of the embryos the brain had not been injured at all, but the prick had destroyed the nose only. This experiment shows conclusively that it is the absence of tissues between the eye anlages that allows them to come together and unite, and that a rudimentary brain is unnecessary. The experiments of Harrison and of Lewis have not been published, and with their permission I have made this note of them.
‘Born, Roux’s Archiv, IV, 1897. 'Speman, Roux’s Archiv, XV, 1903, and Zool. Jahrbﬁeher, VII, Supplement, 1904. ‘Levy, Roux’s Archiv, XX, I906.
Finally, since the above was written, the remarkable experiments of Stockard,‘ of New York, made their appearance. Stockard found by placing the eggs of Fundulus into a solution of MgCl2 that 50 per cent of them develop cyclopia. In them the two optic cups wandered towards each other and united, much as was the case in Lewis’ specimens in which the embryonic shield had ﬁrst been pricked. The union of the two cups formed a large compound cup, which in turn derived its lens from the epidermis immediately over it in the middle line of the embryo. How the magnesium acts upon the embryo is not clear from Stockard’s description. No doubt it will be found that it retarded the growth of the frontal process much as is the case in Lewis’ experiments. However, the salt acted also upon the whole body of the embryos, for their development was retarded, making them smaller than usual, and their circulation was feeble, but they did not die. In them, as in Lewis’ experiments, the growth of the brain was normal.
The remarkable experiments of Stockard set at rest all germinal theories of cyclopia, and prove that every egg has in it the power to develop cyclops monsters.
At any rate, these experiments, as well as the numerous pathological embryos with deformed heads and faces, prove that there is an extensive destruction and shifting of tissues in the formation of monsters. This is also well illustrated in the production of club—foot in the human embryo. It has frequently been noticed that tadpoles whose development had been arrested formed stubby or club tails and ﬁns, a condition that corresponds well with club-shaped extremities in man. In my collection there are eighteen embryos with deformed legs or feet, ranging from the very earliest period
‘Stockard, Roux’s Archiv, XXIII, I907. 48 MALL. [VoL. XIX.
until the foetus is well formed. The leg bud is ﬁlled with condensed mesenchyme and is irregular in shape, sometimes being stubby on one side of the body and normal on the other. The study of the larger embryos shows that there is a kind of “inﬂammation” in the deformed extremity, there being an “inﬁltration” of cells, which is especially well marked in the tendons and around the cartilages. In general, this condition may be accounted for by a general arrest of development due to impaired nutrition. At any rate, embryos that are not developing well, experimental larvae, and human embryos with other malformations, often have club-shaped arms, legs, ﬁns and tails.