suffice to eliminate latent morbid tendencies, or secure absolute relief from a confirmed source of functional disturbance. And the more we investigate the causes of chronic diseases, the more we shall find them depending as much upon atmospheric agencies acting silently but constantly, as upon special habits of life.* The question in every case must finally resolve itself into this, viz.: whether the climate be, or not, suited to the individual constitution; because, if not, it is vain to expect continuance of health. No organism can resist the antagonism of the imponderable agents, particularly when aided by allies within it.

In connection with climate, also must be considered those seasonal changes, which act both as exciting causes of disease, as well as predisposing ones by repetition. Hence, while a simple exaggeration of seasonal conditions might excite disease chiefly in the weak and invalid, a cycle of seasons of unusual temperature would finally tend to lower the vital powers of even the strongest, and so create an epidemic constitution in all. The doctrine of cumulative influences is, perhaps, one of the most neglected chapters in General Pathology; and yet, if correctly studied, it may be made of lasting importance, as one of the bases of prophylaxis. We know, for example, that a European cannot long reside in the tropics without incurring an attack of endemic fever, or suffering from

latter by this sum, we can deduce the time approximately of a complete reconstruction of the body by metamorphosis of its particles. * Dr. Henry J. Bowditch, of Boston, has well shown this in a monograph entitled, On Consumption in New England.-Boston, 1862. + See Cyclical Changes, by Dr. E. Smith, London, 1861, p. 356.

derangements of the liver. He may escape both during the first year, or, perhaps, even the second, but very few escape the third season. Now, during all this time, is it rational to believe that the seasons have suspended their influence in his behalf? Or, has not the system rather been slowly succumbing before the cumulative influences of climate until its limit of tolerance has been reached? If every foreigner could be transported home at the end of a year, and rehabilitated physically, why might he not perpetually escape this point of saturation? The inhabitants of the plains in India fly to the mountains during the summer months; our Southern fellow citizens come North likewise to escape the malignant fevers of their own homes; and all see and approve of the wisdom of this course. But, inside of such potent necessities for removal from notoriously unhealthy localities, there are silent, insidious causes at work in every climate, which, in relation to particular organisms, are as surely fatal in tendency as the most malignant of acute diseases. This law explains to us the disadvantage under which all medical treatment labors, when addressed in situ to diseases born of special local causes and how difficult it is to rally powers that have long been paralyzed; it also shows why the mortality among the poor, from no worse diseases than a better-conditioned class may at the same time be suffering, must always be greater. It is plain that climate acting upon temperaments, and habits of living superadded to these, serve to determine the type which disease assumes in any organism; and if so, then by altering these modifying agencies, we can

greatly mollify the activity of diseases. The type of fever which a sanguine or nervous temperament would develop in Naples or Rome, would be far different from the same disease occurring to the same person in London or Edinburgh. In undertaking to prevent disease, by anticipating and mollifying its predisposing or active causes, we shall find it important to omit none of the agencies, whether inside or out of the body, which I have enumerated.

Another point which offers itself to our notice in this connection, relates to that large class of nervous disorders which are most despotically influenced by the great law of periodicity. This law, which governs all physical nature, bears with peculiar emphasis upon the function of innervation. As all the phenomena of the universe obey its commands, so our instincts, desires, necessities, and diseases, fall within the limits of its orbit, and circulate about its common centre. The doctrine of habit has its foundation here, and by observation of the periodic recurrence of cycles, we can prepare the system to meet, and successfully resist the return of morbid conditions. We easily recognize this rule of physical conduct in intermittent fever, but shall we stop here or search for it also in neuralgia, gout, hay-asthma, epilepsy, mania, &c.? Shall we not find it operating in all the great functions of evolution, in childhood, manhood, and old age, and by its study can we not often repress the tendency towards functional derangements at inopportune moments? How much of disease occurring in childhood, or during pregnancy, or after surgical operations, might not be prevented

by a constant appreciation of the inexorable laws of temperament, climate, season, and periodicity? For the seasons may be made prophylactic agents either by awaiting their return, or going in search of them in foreign parts; temperamental tendencies may be essentially controlled and kept within healthy limits, and the law of periodicity may be stripped of many of its terrors, by the experience of our ability to interrupt its operations, so that debilitating crises of all kinds may be foreseen and prevented. Under this, not altogether theoretical view of the laws of health and disease, there seems to be no good reason why we may not confidently look forward to a time, when we shall think him the greater philosopher, who causes nature to balance her own operations in the human system by the harmony of relation between them, whereby each part being spared the performance of double duty, or the necessity of superfluous friction, may be consumed consentaneously with the rest, and the cycle of life may cease to be abridged by those multiform causes which, partly born of human agency, can most certainly, to that extent, be controlled by it; for increasing experience proves the truism of Seneca: Non accepimus vitam brevem, sed fecimus.

DIET.

The positive relations between food and the wants of the human economy are well understood, physiologically. And when disease has essentially modified the processes of constructive assimilation, we

seek determinately to reëstablish nutrition by special alimentary substances. But before even the actual invasion of disease, conditions of the system are engendered by causes susceptible of being referred to no other agency than food. A recent author, Dr. Chambers,* with true philosophical acumen, has pointed out that the essential cause of disease consists, in a majority of instances, in an excess of destructive over constructive assimilation; and he proves his allegation by a course of treatment specially intended to reëstablish harmony between these two processes. It cannot be too strongly emphasized, that the influences of diet are as cumulative as those of climate, and may tend to produce disease as well as prevent it. Whence it comes that the diet of mothers tells upon the health of children, that of childhood upon the vigor of manhood, and that of manhood upon old age. The call for variety in aliments is not simply æsthetic or artificial, but expresses an actual want of the system to meet daily contingencies in the function of insterstitial metamorphosis; and a neglect to gratify this instinctive admonition, if persisted in, inevitably results in disease. Exclusivism in diet, which is intemperance in fact, produces ill effects upon all who practise it. Of these we have notable example in the tea-and-toast anæmia of poor sewing-women-in the pellagra of the Lombard peasant-the pinta of Mexico, or la carate of Bolivia, all produced by feeding exclusively on maize. The influence of a rice diet in India, upon *Chambers: Renewal of Life.

+ Morel: Degenerescences de l'Espèce Humaine, p. 574.