feature, figure, and habits, have shown singular resemblance in the symptoms of the disorders affecting them, and in their idiosyncrasy as to particular remedies. No new difficulties occur in the explanation of these facts. Every morbid cause must have definite effect on certain parts. of structure; and, if these are alike in two or more individuals from family descent, the presumption is, that any diseased actions ensuing will exhibit corresponding likeness in kind and degree. What here we might expect on theory, we find to be realized in the facts. And connected with these is the result, well attested by experience, that there is a general tendency towards the same duration of life in those of the same family;—often modified or subverted by individual constitution or by the incidents of life, but never perhaps wholly absent. In some instances this may be referred to the likeness in particular structures; but we must probably look still further and deeper for the causes concerned in this remarkable effect. The research indeed brings us immediately to the great mystery of the transmission of life itself;- under the condition of a fixed average duration to each species, and with subordinate variations belonging to particular series in the same species. It is another fact in the history of hereditary diseases, meriting attention on various accounts, that many of these have a well-marked tendency to evolve themselves at particular periods of life, differing for each. This is true, not only as to those which are termed constitutional, such as gout and scrofula, where it might more easily perhaps be anticipated, but applies also to some cases where the hereditary disposition seems limited to a particular organ, as the heart, the liver, or the brain. These circumstances find their explanation in * I find some curious instances to this effect recorded by Boerhave ; "Novi in hac urbe familiam, in quâ omnes certâ ætate schirrum accipiunt, the general views already stated. When the disease depends upon anormal conformation of some organ, it may be brought into active shape, either by the accumulated effect of exciting causes long continued, or by the operation of new causes, coming into operation at certain periods of life. If there be cases in which we may suppose the blood concerned in transmitting hereditary taint, a point already considered, still it is conceivable (especially as we know that this fluid undergoes actual alteration at different ages) that some changes in its quality or distribution may bring the morbid principle into activity at one time rather than another. Or, without referring to such direct alteration in the blood itself, the changes successively taking place in the solid tissues of the body, particularly those of secretion, may so operate upon this fluid as to cause the commencement at a certain period of morbid changes, whether of deposit or other kind of action, which had not before occurred. To seek to carry explanation beyond these very general views would be merely to substitute vague phrases for actual knowledge. I have not hitherto alluded to the question, which has been discussed and differently answered by different authors, from which parent the predisposition to disease is more frequently derived? The difference of opinion here probably results from the actual approach to equality in the occurrence of the respective cases. The question, in fact, merges in the more general one as to the transmission of physical resemblances from parent to offspring; these being, as we have seen, the chief source of similarity in morbid affections. And et hoc malum ab ovo parenti liberis est communicatum ;-uti et familiam, ubi omnes certâ ætate icterum accipiunt, et sic orto postea hydrope, moriuntur. Novi etiam aliam familiam ubi omnes primò satis faceti, sed certâ ætate in melancholiam incidunt."— Boerhav. Prax. sect. 485. as such resemblances, both of lineament and structure, proceed from each parent, according to laws of which we are ignorant, but seemingly in proportion nearly alike, the diseases therewith connected must be considered under the same relation, and as being probably derived equally through the two sexes. * Viewing the subject of hereditary disease in all its parts, one question yet arises: viz. whether, and to what extent, there may be a continued progress of change in the organization, or other material cause of disease, through successive generations?-or, where are the limitations to such changes, and whence derived? The general answer to this question may be drawn from the views already stated; and particular facts in illustration of it are best deduced from the growth of varieties in animals and plants, whether casual or designed. The conclusion presumably is, that the repetition of circumstances producing variation tends in itself to augment or confirm this, whether disease be the effect or not;—but that the original type of the species is ever present in opposition to the changes thereby induced; defining their extent, differently perhaps for different parts of the structure, but still with an eventual and certain limit to all. It is unnecessary to point out the important relation to practice of all that concerns hereditary tendency to disease. The subject is one which meets us at every step, and to which our attention is perpetually required, as an exponent of symptoms, as affording some of the most certain means of prognosis, and as directing us in many particu * Dr. Nasse, of Bonn, treating of the tubercular diathesis, considers that the disposition to disease is more commonly derived from the mother than the father. The general opinion seems to have been the reverse of this; but neither view, as far as I know, is supported by such amount of averages as to warrant its adoption. lars to the right course of treatment. No judicious physician will neglect the resources hence derived, which are in truth essential to sound and successful practice. It is probable they will be largely augmented in future, both by more exact and ample observation of facts, and by the extension of our knowledge of principles in this remarkable branch of physiology. There is yet wanting to our medical literature a work which may embrace the subject in its whole extent, and with the aids derived from other departments of science. What I have given here is but an outline of this; and the examples are drawn chiefly from my own observations in practice. These of course might be greatly extended in number and variety, as well from the results of individual experience, as from research, even the most superficial, into the writings of medical authors.* I must add, however, that an inquiry so instituted, would require much more specification and exactness than I have been able to give in this general view. It is not enough, for instance, to speak of diseases of the heart collectively, at a time when the morbid anatomy of this organ is minutely investigated, and averages of weight and admeasurement obtained for its different states. And it will be readily perceived that the more precise and minute the definition of parts subject to hereditary affection, the greater is the hope of further insight into this remarkable phenomenon, the more certain the aids afforded to the treatment as well as theory of disease. * In looking over the works of Morgagni, for example, I have been struck by the number of cases of hereditary disease to which he incidentally refers; rendered more valuable as instances by his exactness as a narrator. 44 CHAP. III. BLEEDING IN AFFECTIONS OF THE BRAIN. Is not depletion by bleeding a practice still too general and indiscriminate in affections of the brain, and especially in the different forms of paralysis? I believe that the soundest medical experience will warrant this opinion. The vague conception that all these disorders depend upon some inflammation or pressure, which it is needful to remove, too much pervades and directs the practice in them: and, if the seizure be one of sudden kind, this method of treatment is often pursued with an urgent and dangerous activity. Little heed is taken of the many cases where the symptoms depend upon irritation alone, - or on loss of nervous power, -or on deficient circulation of the blood within the brain, or on altered qualities of this blood,-or, it may be, on morbid changes in the nervous substance itself. Theory might suggest that in some of these various cases, the loss of blood would lead to mischief. Experience undoubtedly proves it; and there is cause to believe that this mischief, though abated of late years, is still neither infrequent nor small in amount. -- It is certain indeed that there is a state of brain, best perhaps represented to us in its general effect of diminished nervous power, which tends to produce sometimes spasmodic seizures, sometimes delirious or maniacal affections, sometimes palsy of different parts of the body—these effects being in no wise obviated by depletion, but rather increased by all such means; while they are relieved by remedies which tend to |