most recently occurred to me, I find three cases, including one of the morbus cœruleus, in three successive generations. It is unnecessary to add others.

Of hereditary obesity I have seen some very curious examples; -- the most recent that of a family, in which, out of two generations, four individuals died of the results of excessive accumulation of fat, producing diseased action of the internal organs, and dropsical effusions, two other cases of the same tendency existing in the family under less urgent form.

-

Several cutaneous disorders evidently tend to become hereditary; whether from peculiarity in the texture of the skin, or depending on the general temperament and state of the circulating fluids. I have lately seen three cases of psoriasis in the children of a family where there is strong predisposition to gout; a conjunction I have observed in many other instances. Certain impetiginous eruptions belong also to a family constitution, such as is often termed scorbutic, and are obviously transmitted from parents to children. Icthyosis is occasionally seen as an hereditary disorder.

I may notice here another singular disease, the Pellagra of Lombardy, in which, together with the peculiarity of a local limitation, there occurs a very singular succession of symptoms; beginning with a cutaneous affection of leprous character, passing through various stages of cachectic disorder, and ending generally, after the lapse of a few years, in fatuity or death. I have had much opportunity of observing this curious disease in all its forms.* There can be no doubt of its here

* A paper I wrote on the Pellagra was published in vol. viii. of the Medico-Chirurgical Transactions. There are many points of great interest in the history and pathology of this disorder. Its first appearance seems to have been in the Alto-Milanese; but in the early part of this century, it had spread increasingly over the greater part of Lombardy, and to the

ditary nature, though there is difficulty in tracing it back in Lombardy for more than eighty or a hundred years, and equal difficulty in assigning the causes which give it existence in this district alone.

Diabetes, from my observation (and Dr. Prout states the same fact) has sometimes an hereditary character. Eneuresis in children, from whatever source arising, occurs sometimes in so many individuals of the same family, as to make it almost certain that it has a common congenital origin. What is not less remarkable, as an instance of similar specialty, emphysema of the lungs has been ascertained to depend in the majority of cases on hereditary influence, independently of any disposition to tubercular pulmonary disease.*

Another instance, which may be termed special, though belonging to a part of structure diffused over the whole body, is the hæmorrhagic diathesis. Though I do not find in my notes any well marked examples of its hereditary nature, except where confined to the lungs and connected with phthisical constitution, yet some are recorded so explicit as scarcely to leave the fact in doubt; and remarkable further, from the seeming limitation of these instances to the male sex. Nor is there greater difficulty of explanation here, than where a more limited portion of structure is concerned. The points of question are the same in each case; and the solution, if ever obtained, must be common to both.

shores of the Adriatic Sea. I have seen the disease as far eastwards as Friuli, at the foot of the Carinthian Alps. There are some districts in the Alto-Milanese where the pellagrosi form one fifth or sixth of the whole population. And at the time I visited the Lunatic Hospital at Milan, out of nearly 500 patients of both sexes, about one third had been brought thither in effect of this disorder.

* This fact we owe to the late Dr. Jackson, of Boston in America, a physician whose life was too early terminated.

Other diseases might be mentioned, offering questions no less difficult than those stated above. Asthma, for example, sometimes shows an hereditary character. I have known the complaint to occur in three successive generations; and often so numerously in the same family as to make it certain that a common cause was concerned. This cause is presumably one of structure:-yet it would be difficult to affirm it to be so, or to state in what part the peculiarity is likely to exist. It may be that some peculiarity of the nervous system is chiefly concerned; and there is nothing to disprove the possibility that irregularity of certain parts of this system may be transmitted by descent, so as to become a source of the disordered actions of asthma. Or the cause may more probably be sought in connexion with the gouty diathesis, to which I cannot doubt from experience that some forms of asthma are closely related.

Every physician will recognize the strong tendency to hereditary character in disorders of the brain and nervous system. This is a very remarkable part of the subject; involving, as it does, every variety and degree of morbid affection, from simple head-ache to the worst forms of epilepsy, apoplexy and palsy. I shall hereafter notice, in relation to another part of the subject, some singular examples in its illustration. The topic is further one of deep interest, as including the various conditions of hereditary insanity,instanced not merely in particular families, but even in districts and communities, where from local circumstances there has been little intermixture with the rest of the world. From the latter disease thus occurring, we gather the important conclusion, that some deviation in physical structure, whether obvious or not, is the cause of the aberrations it presents. In no other way can we conceive the transmission of the tendency from one generation to another. It may be

that a part of the fabric of the brain is concerned, far too minute for the most subtle research to follow: and this indeed might be presumed, looking at the nature of the functions affected. But still, whenever the transmission occurs, we are bound by all analogy to infer the presence of a morbid material cause, upon which the phenomena primarily depend.

There is much that is curious in the tendency to head-aches thus transmitted by descent, and often going through whole families with similar character. The cause here presumably varies in different instances. Sometimes, and especially perhaps where they are periodical, the affection may belong to the gouty habit, and to the matter of gout in the circulation. In other cases, anormal structure of the vessels of the head may be concerned; in others, again, some peculiarity in the nervous substance itself.

In hereditary affections of the nerves, as in those of other parts, it is extraordinary in what minute peculiarities the tendency often shows itself. It is difficult indeed in some of these cases to distinguish what is due to imitation alone: but in other instances, where this is excluded by circumstances, we find nevertheless nervous habits and disorders of the parents reappearing in the offspring to a singular extent. These entailed disorders are certainly more numerous than is generally supposed; and probably the source of many morbid states, apparently remote in kind. As respects their origin, they may all be referred to the general principles we have already laid down.*

There are some examples of anormal structure or disease,

* Among particular forms of hereditary mental disorder, the tendency to suicide is recorded on what seems to be sufficient evidence. Curious examples to this effect are given by Pinel, Dr. Burrows, and Dr. Rush of Philadelphia.

which, though frequently occurring in detached instances, yet are so especially numerous in certain localities, as to afford suspicion, in the absence of other sufficient causes, that hereditary tendency is much concerned. Such is the goitre of particular districts, no consistent explanation of which has yet been given, founded on local circumstances of climate or mode of life. The Plica polonica, prevailing almost exclusively along the course of the Vistula, is another instance to the same effect. I might apply the same remark, though with greater doubt, to that curious affection, the Trismus nascentium, prevalent in particular localities, and these widely different in all physical circumstances. The great frequency of stone in the bladder, in certain districts where there is no obvious peculiarity of air, food, or water, as a probable cause; and the common tendency to lithic acid deposits in the same family, may admit of like explanation. And this is further sanctioned by the certain connexion of the calculous with the gouty diathesis.

Seeking then for the most general expression of facts, we may affirm that no organ or texture of the body is exempt from the chance of being the subject of hereditary disease. Or, in other words, every part is susceptible of deviations from the normal type or natural structure, capable of being

When in Iceland, in 1810, I had the opportunity of collecting some facts as to the singular frequency of this disease in the Vestmann Isles, on the southern coast of this island. On these desolate rocks, the population of which does not exceed 160 souls, I found that, in a period of 25 years, 186 infants perished of this disorder, under the age of 21 days; of whom 161 died between the fourth and tenth days after birth; 75 on the eighth day. Though the condition of life of these poor people is singularly destitute, fish and the eggs of sea-fowl being their sole aliment, yet is it not so different from that of the Icelanders of the main land as to explain the frequency of this fatal disorder among them; and it would seem as if some constitutional and hereditary causes were concerned.