Imágenes de páginas
PDF
EPUB

are of the type simplex X simplex, and the findings would seem to indicate that all the matings are of this type.

DUPLEX X DUPLEX. Under this type of mating we have grouped all those fraternities in which both parents are recorded as normal.

In the study of seventy-six fraternities there were 441 conceptions; 62 are too young for classification or entirely unknown, 103

[merged small][ocr errors][merged small][ocr errors][ocr errors][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Fig. 10.

This chart shows the mating of two normals. They each have defective relatives. Of the seven children the fourth is an epileptic and the others seem to be normal. E, epileptic; F, feeble-minded; A, alcoholic; N, normal. Case 2,983.

died before the age of 14 years. Of the 276 others, 172 are normal, 75, or 27 per cent., are epileptic and 3, or i per cent., feeble-minded, with i insane and 25 tainted, that is, 197 ( 172 +25), or 71 per cent., are duplex or simplex in character. (Fig. 10.)

The results show that these normal parents are not duplex, but simplex, and a study of their ancestors justifies this conclusion, for in at least 45 of the matings, one or both of the parents descended from tainted ancestors.

PROC. AMER. PHIL. SOC., LI. 205 J, PRINTED JULY 23, 1912.

All the available facts point toward the conclusion that the various common types of epileptics seen in institutions lack some element necessary for complete mental development, which is also true of the feeble-minded.

Two epileptic parents produce only defective offspring, when both parents are either epileptic or feeble-minded, their offspring are also defective, the defect taking the form of epilepsy, feeblemindedness or some other neuropathic condition. This is also true of feeble-minded parents.

In the light of our present knowledge, the results obtained from the study of our data do not justify the classification of the reported normal parents of epileptics as duplex. We are forced to the belief that their germ plasm is simplex, and feel confident that more complete data would show the taint in their ancestors.

Our data seem to support the belief that alcohol is a cause of defect, in that more children of alcoholic parents are defective than where alcoholism is not a factor.

That there are more than five times as many epileptics as feebleminded persons in those fraternities coming from matings where neither parent can be classed as normal, or called mentally defective, seems to indicate that neurotic and otherwise tainted conditions are more closely related to epilepsy than to feeble-mindedness. NEW JERSEY STATE VILLAGE FOR EPILEPTICS,

SKILLMAN, N. J.

IS THE CONTROL OF EMBRYONIC DEVELOPMENT

A PRACTICAL PROBLEM?

BY CHARLES R. STOCKARD.

(Read April 19, 1912.)

Under favorable natural conditions two normal parents should, and usually do, produce a vigorous normal offspring. When, however, the conditions of development are modified or if in the second place the parents are not entirely normal the offspring is usually more or less defective. I shall attempt to show that the proper development of the offspring is dependent upon two main factors, first the physical qualities of the parental germ cells, and second the environment in which the embryo develops.

One is at first sight apt to think that deformities and defects are rare among men and other animals; but closer observation will show that the really structurally perfect individual is rather exceptional. Gross anatomical defects or monstrosities are frequently found among all animals, while lesser defects of minor importance are to be observed in a majority of individuals. These defects often cause no inconvenience, and indeed, we may be ignorant of their presence, since they are generally internal. Yet many apparently normal individuals sooner or later suffer or may actually die from some hidden developmental imperfection. The well-known congenital defects of the heart and other parts of the vascular system, digestive tract, etc., as well as the numerous developmental arrests in various parts of the body constantly remind the observer of the great loss in ability and energy that the race suffers as a result of faulty development.

These defects in construction must be considered a disease which causes the death of about 23 per cent. of the human race before or shortly after the time of birth (Sullivan's studies and French statistics), and handicaps a certain proportion of the survivors through

out their lives. We carefully study and use all known precautions to protect ourselves against post-natal infections and diseases, and much interest and time is given to combating the causes, yet little is said and scarcely anything done towards a control of development, or the hygienic protection of the developing individual.

This is really a morphological problem and is as truly a part of the fight against disease as is the treatment of abnormal physiological processes. It is not all of morphology to describe and study the detail of bodily structure, but its important task is to understand and analyze that structure, and if possible control and regulate its formation: and thus, if properly developed its goal is to relieve the race of its great structural disease-a disease which affects more individuals than any other one malady of man.

To most persons the above task seems at first thought a futile undertaking, and any one suggesting such control or preventive treatment might be interpreted as indulging in fanciful speculation. Yet the data available from the studies of defective persons in different countries of the world, and the experimental evidence furnished by work on lower animals makes the correction or prevention of developmental defects seem even today a problem to be practically handled to a slight degree at least.

To proceed as with any other disease, we must first ascertain the cause of these conditions, as the possibility of a cure depends upon the nature of the cause.

Are monstrosities and defective development due to some innate change within the germ cells of the parent, thus being incurable, as many former workers would have us believe? Or, are they due to changes produced in the germ cells by the action of some unusual condition in the body of either the male or female parent, or finally may they not be due to an unusual environment acting upon the developing embryo itself? In both of the latter cases the conditions are open to regulation or control. These questions may only be solved experimentally and the experiments have proven that the great majority of monsters are due to the action of unusual conditions upon either the parental germ cells or the developing embryo. There may be some changes of form or variations in animals which are due to

innate changes in the germ-plasm but even these when fully understood may possibly be shown to result indirectly from some change in the chemical surroundings.

First to consider the modifications induced in the developing egg or embryo by a strange chemical environment. It has been found for the eggs of a number of animals that develop normally in seawater that when certain chemicals are added to their environment they develop into various unusual forms.

I experimented for several years on fish's eggs and found that on adding any one of a large series of salts to the sea-water that the eggs developed abnormally and gave rise to a great number of monstrous individuals. The types of the monstrosities were variable, and the same kind of monster often resulted from different treatments. This was to be expected, but the important problem was to produce some definite type of monster in great numbers with any given treatment. This I finally succeeded in doing and in some experiments got as many as 90 per cent. typical cyclopean or monophthalmic monsters. These types of monsters first occurred in solutions of MgCl, in sea-water. In such solutions as many as 50 in 100 eggs formed one-eyed cyclopean embryos. Since Mg has the power to inhibit activity in animals and so acts as an anæsthetic I determined to try the action of a number of such substances on the developing eggs to ascertain whether they might also inhibit the lateral migration of eye parts. Alcohol, ether, chloroform, chloreton, etc., were employed and cyclopean monsters resulted from eggs developing in all of these substances. Alcohol gave the most decided effects and inhibited the normal production of eyes in almost all cases. All of these anæsthetics act more particularly upon the central nervous system of the adult and it is important to find that the development of the nervous system is also especially affected by them. In alcohol solutions the embryos showed almost every gross abnormality of the brain which is known to occur, and the spinal cord was often defective.

I have repeated the experiments of Féré with hen's eggs and find that when these eggs are exposed to fumes of alcohol many abnormal chicks result. When hen's eggs are placed in closed dishes over

« AnteriorContinuar »