of them fatal in result. In another instance, four cases of ascertained disease of the heart, all fatal about the same period of life, occurred to my notice in the brothers and sisters of one family; without any suspicion, as far as I could learn, of the parents having been the subjects of this disease. In the instance of the deaf and dumb, already referred to, the examples are frequent and curious of several children being thus affected, (five out of a family of eight, four from a family of seven,) without similar defect existing in the parents. In one family with which I am acquainted, three children out of five are dumb, and of deficient intellect, but without deafness, there being here also no record of the like defects in the families on either side. At the School for the Deaf and Dumb in Manchester, in 1837, there were forty-eight children, taken from seventeen families; the total number of children in these families being 106, and giving therefore an average of nearly three such cases in each family. Out of these instances, there appears but one in which the defect was known to exist in either parent; and we may rightly therefore consider this as one of the most striking examples of the fact under consideration. As a curious variation of the same general conditions, a case is known to me, where the children of parents, each deaf and dumb, are themselves free from that defect. In another large family I have known almost every child short-sighted, without either parent being so.

Some of these examples may probably be referred to the condition last mentioned, of the revival of an hereditary disorder; absent, as far as outward appearance goes, in one or more generations. But proof to this effect is wanting in other cases: and the remarkable fact remains, of several children of the same parents being affected in common with a given malady, of which there are no certain prior examples in either family. The extent and sudden development of

disease in these instances may in itself be taken as the proof of new elements being introduced.

All physiology is at fault as to the solution of this phenomenon. Nor in a matter so obscure, can we venture beyond the inference, that where each parent is capable of conveying certain characters of resemblance, physical and moral, to their offspring, the combination of these generative elements, whatever they be, must have effect, more or less, in modifying the result. This presumption does not go beyond the fair bounds of reason; is justified by various experiments on other animals; and may afford the clue, under future observation, to some of the most remarkable facts in the physiology of man.

A yet further variety in the hereditary transmission of disease is its limitation, more or less complete, to the males or females of the family affected. This fact is illustrated by two or three of the instances already given, and seems well attested in the case of the hæmorrhagic diathesis.* In the more familiar example of gout, the same condition may be admitted to a greater extent. The circumstance most remarkable here is the frequent evidence of transmission through the female of a morbid tendency or action, not observable in herself during any part of life. This indeed is only a case of the singular phenomenon of atavism, already noticed; but still more interesting to physiology, as being more special, and including the relation of the sexual peculiarities to the other functions and changes of the system. Considering the subject in its most general light, it appears certain that the cause of

* Examples to this effect will be found in the Archives Générales, Oct. 1833, and July 1835; one or two of them made more remarkable by the transmission of the diathesis through females, themselves unaffected in this way; and further by the very frequent concurrence of the hæmorrhagic with the rheumatic constitution.

action in such cases cannot be altogether dormant, though not attested by the usual signs of its presence. We may better find explanation in differences of the seat and manner of action, whether depending on sexual structure, or on other less obvious conditions. It cannot be doubted that such differences exist, modifying the influence of every one material agent upon the body; and thereby giving, it may be presumed, a totally different aspect to the effects of the same physical cause. I shall have other occasions to remark on the wide application of this principle to the phenomena of disease.

Looking at what may hereafter be learnt on these curious subjects, the most obvious source of knowledge is the observation of corresponding facts in other animals. Here our means of inquiry are greatly increased by adding direct experiment to the mere observation of facts. The results obtained from breeding, especially in the domestic animals, are infinitely valuable in this respect; and replete with curious inferences, all more or less applicable to the case of man, though, from some cause or other, they have been less closely applied to this illustration, than their importance might warrant. The whole subject of specialties of structure and function, whether natural or obtained by artificial means, is full of the same interest; and forms the most direct line along which to carry research into the types and development of animal life. The physiology of plants affords similar illustrations; though more remote, from the wider difference in their organs and mode of existence. Much has been attained on these sub

* I may cite, as an excellent example of the mode of pursuing this research, the work of Gallesio, little known in this country, "Storia della Riproduzione Vegetale." Pisa, 1816. Gallesio takes the genus Citrus as his subject, and, from his experiments upon these plants, draws conclusions which apply largely to the production of varieties, monsters, and hybrids, in vegetable life.

jects; but more yet remains behind. Though the principle of life and reproduction is still a mystery at the root of the inquiry, all the effects resulting from this principle may become better known, their connexions determined, and the relations explained by which they take the forms of hereditary disease.

In a former part of this chapter, I have adverted to the strong hereditary tendency in disorders of the brain and nervous system, and to the many remarkable results thereon depending. It would be impossible in a general view like the present, to pursue this subject through its many bearings, interesting though they are to all the conditions of life and human society. Here indeed, as so often before, we are called upon to note the close relation of particular morbid phenomena to more general laws; and, in the present case, to those laws which determine the varieties of character in nations and communities of men. Hereditary deviations in excess, such as come under the character of insanity, are corrected or limited by the usages of society. Those variations from the common type (if we may apply this term to mind as well as body) which are not so controlled, may, in the infancy of any community, and in combination with other causes, become the basis of those more permanent traits which we designate as the character of a people. Such diversities existing, as they actually do, and being in many cases perpetuated within human record, must be derived in some part from this source. Or if we could suppose it otherwise as to origin, it must at least be admitted that this cause is concerned in their perpetuation among races of men.

As another remarkable fact connected with this subject, I may mention the frequent occurrence of an hereditary temperament, in which are blended together the elements of

various disease, both of body and mind, with some of the highest mental qualities and endowments. Instances are frequent, where in the same family we find almost every individual possessing some strongly-marked peculiarity; such peculiarities often very different in aspect, yet all having reference to some single point in constitution from which the several effects diverge. Or the life of one individual, so circumstanced, may itself afford example of the most singular extremes of state, equally to be referred to some common

cause.

Another fact still to be noticed regarding hereditary constitution, in its relation to disease, is, the disposition of individuals of the same family and generation to be similarly affected under any given maladies; even such as have no apparent connexion with the peculiarity of family habit. There are indeed various chances of error in observations of this kind; and many exceptions will occur. Nevertheless, examples free from ambiguity must be familiar to every medical man, where disorders assume a certain marked character in the same family, as regards the severity of the symptoms, the organs especially attacked, and the effects they leave behind. Such is the case with hoopingcough and various infantile complaints,—with exanthematous and epidemic diseases, and with others less definite in their course of symptoms. In the instance of twins (the frequent occurrence of which may itself be noticed as a peculiarity in some families), these coincidences show themselves in still more remarkable degree. And it is likely, in general, that they should be most distinct in early life, when extraneous causes have yet done little to alter congenital likeness in struc

ture and habit.

I find in my notes some curious instances, where two children of a family, with strongest likeness to each other in