pear to any one to be fabulous, we might adduce the testimony not only of the whole people who dwell on the coasts of England, Ireland, and Scotland, but also that of the illustrious historiographer Gyraldus, who has written so eloquently of the history of Ireland, that the barnacles are produced in no other way. But since it is not very safe to trust to popular reports, and as I was, considering the singularity of

"They spawne, as it were, in March and Aprill; the Geese are found in Maie and June, and come to fulnesse of feathers in the moneth after. And thus hauing, through God's assistance, discoursed somewhat at large of Grasses, Herbes, Shrubs, Trees, Mosses, and certaine excrescences of the earth, with other things moe incident to the Historie thereof, we conclude and ende our present volume, with this woonder of England. For which God's name be euer honoured and praised."-(GERARDE, "Herball," 1633.)

the thing, rather skeptical even with respect to the testimony of Gyraldus-while I was thinking over the subject-I consulted Octavian, an Irish clergyman, whose strict integrity gave me the utmost confidence in him, as to whether he considered Gyraldus worthy to be trusted in what he had written. This clergyman then professed himself ready to take his oath upon the Gospels, that what Gyraldus had

recorded of the generation of this bird was most true; for he himself had seen with his eyes, and also handled those half-formed birds; and he said further that, if I remained a couple of months longer in London, he would have some sent to me."-(TURNER'S " Avium Præcip. Hist.," art. "Ansr.")

But the writer to whom we are most indebted for authentic information upon this interesting subect is Gerarde, the father of English botany, and author of the "Herbal," a ponderous work of 1,500 pages, from which the cut Fig. 2 is taken. He says: "What our eyes have seen, and hands have touched, we shall declare. There is a small island in Lancashire, called the Pile of Flounders, wherein are found broken pieces of old and bruised ships, some whereof have been cast thither by shipwreck, and also the trunks and bodies, with the branches, of old and rotten trees, cast up there likewise; whereon is found a certain spume, or froth, that in time breedeth unto certain shells, in shape like those of the mussel, but sharper pointed, and of a whitish color, wherein is contained a thing in form like a lace of silk finely woven, as it were, together, of a whitish color; one end whereof is fastened unto the inside of the shell, even as the fish of oysters and mussels are; the other end is made fast unto the belly of a rude mass or lump, which in time cometh to the shape and form of a bird. When it is perfectly formed the shell gapeth wide open, and the first thing that appeareth is the aforesaid lace or string; next come the legs of the bird hanging out, and as it groweth greater it openeth the shell by degrees, till at length it has all come forth, and hangeth only by the bill. In short space after it cometh to full maturity, and falleth into the sea, where it gathereth feathers, and groweth to a fowl bigger than a mallard and lesser than a goose, having black legs, and bill or beak, and feathers black and white, spotted in such manner as our magpie, called in some places pie-annet, which the people of Lancashire call by no other name than tree-goose; which place aforesaid, and of all those places adjoining, do so much abound therewith, that one of the best is bought for threepence. For the truth thereof, if any doubt, may it please them to repair to me, and I shall satisfy them by the testimony of good witnesses."

Again says Gerarde: "The historie whereof to set foorth according to the woorthiness and raritie thereof, woulde not onely require a large and peculiar volume, but also a deeper search into the bowels of Nature than my intended purpose wil suffer me to wade into, my insufficiencie also considered, leaving the historie thereof rough-hewen unto some excellent men, learned in the secrets of Nature, to be both fined and refined; in the mean space take it as it falleth out, the naked and bare truth, though unpolished."

When the Royal Society of England had been established fifteen years, this fable was accepted, and described in the philosophic transactions, in 1677, by Sir Robert Murray, who says: "Being on the

island of Uist (East) I saw lying upon the shore a cut of a large firtree, about two and half feet in diameter, and nine or ten feet long, which had lain so long out of the water that it was very dry, and most of the shells that had formerly covered it were worn or rubbed off. Only on the parts that lay next the ground there still hung multitudes of little shells. This barnacle-shell is thin about the edges, and about half as thick as broad. Every one of the shells has some cross-seams or sections, which, as I remember, divide it into five parts. These parts are fastened one to another with such a film as mussel-shells have. These shells are hung at the tree by a neck, longer than the shell, of a kind of filmy substance, round and hollow, and curved not unlike the windpipe of a chicken, spreading out broader to where it is fastened to the tree, from which it seems to draw and convey the matter which serves for the growth and vegetation of the shell and little bird within it. In every shell that I opened I found a perfect seafowl: the little bill, like that of a goose, the eyes marked, the head, neck, breast, wings, tail, and feet formed; the feathers everywhere perfectly shaped, and blackish-colored; and the feet like those of other water-fowl, to my best remembrance."

Many conjectures have been offered as to the origin of this strange myth, and Max Müller suggests the hypothesis that it came from the early misapplication of terms. He remarks: "No man would have suspected Linnæus of having shared the vulgar error, nevertheless he retained the name Anatifera, or duck-bearing, as given to the shell, and that of Bernicula, as given to the goose."

ALTERNATIONS IN THE INTENSITY OF DISEASES.

FROM THE FRENCH OF ALPHONSE DE CANDOLLE.

TRANSLATED BY H. H. W.

HE diminution of the efficacy of vaccination, as a preservative

x, at first of

and afterward of surprise, to the medical world, and even to the nonprofessional public. The causes of this change have been sought in the nature of the vaccine matter. But it has not been demonstrated that taking the matter anew from the cow is to restore the primitive efficacy of the remedy.

Without wishing to call in question with the profession the chances of discovering an explanation, drawn from the domain of medical and physiological facts which they occupy, I desire to point out a consequence of the fundamental law of heredity, as applied to the phenomenon in question. In order to understand the subject in its true

aspects, it will be well, in the first place, to recall a fact in relation to epidemics.

Medical history proves, on the subject of epidemic and contagious maladies, a marked fatality at the time of their first appearance, followed by slowly-decreasing violence from generation to generation. In our own memory the epidemic visits of cholera have diminished in frequency and intensity within a short period of time. Previously to our day, syphilis and varioloid, two infective diseases, differing in their nature, and in their modes of transmission, had presented the same phenomenon-Extreme intensity at the beginning, diminution from period to period.

If this diminution belonged to the nature of the maladies, populations infected for the first time in the nineteenth century should have suffered less than those infected in previous centuries. But this is not what has occurred. When a savage population has recently been visited, for the first time, by the infection of small-pox, it has suffered as much as the Europeans at the beginning of the malady in Europe. It is the fact of invading a new field which renders epidemics destructive. Upon a little reflection, the reason of this is easy to comprehend.

When an epidemic falls upon a population for the first time, the greater part of the individuals disposed to receive the disease are attacked. They die in great numbers. Subsequent births are the offspring of persons who did not contract the disease, or, at the least, who contracted, yet survived it; that is to say, of persons better constituted than others to resist the disease. By virtue of the ordinary resemblance of children to their parents, the new generation will be less disposed to suffer from the epidemic. There will be then a diminution of the violence of the disease, or a temporary disappearance. For the most part I presume a diminution, because that the resemblance of children to their grandparents (which is called atavism) is not very rare, and tends to reproduce certain forms or physiological conditions in families. At the end of two or three generations, that special cause for the return of the epidemic is less felt, the resemblance to a great-grandfather, or ancestor still more removed, being more rare than the resemblance to a grandfather. But then the bulk of the population will no more have been exposed, by itself, or by its fathers and mothers, to the malady in question, or will have been but slightly exposed. Thus is constituted anew, by the very purity of the disease, a proportion of individuals who have not been submitted to the proof of the infection, or of whom the parents have not been submitted to the test; a proportion on whom the malady will be severe, and among whom the law of selection will recommence to operate.

The law of events (force des choses) introduces then a variation in the intensity of every disease, except that it does not act upon diseases of which people rarely die, or which fall principally upon the

aged. The more fatal a disease among youth, the quicker is the work of the law of selection, and the more prompt the diminution of the malady. If a first invasion, for instance, destroys a moiety of the population below marriageable age, the survivors should be very little liable, in their physical or physiological conditions, to the disease, and the children born to them will profit by their immunity. If the disease is less fatal, the purification will be less. We thus discover, I do not say the cause, but a cause why pestilences and other very serious maladies attack populations at intervals, and are, as it is said, epidemic; while certain diseases less serious, even among maladies which attack youth, rule from year to year in a mode more continuous.

Such are the clear laws-one might add the rigid laws-which rule in diseases, to produce aggravation or diminution, independently of all these natural circumstances. Without doubt there may be other circumstances, physical or physiological, and physicians may discover preventive or curative means which exert influence upon them. But the incessant effect of heredity, and of the law of selection, exists, notwithstanding; and, when other influences cannot be demonstrated, we may be assured that heredity and selection perform their part.

We now see that the efficacy of preventive means, such as vaccination, should also vary. When Jenner discovered the utility of vaccination, the small-pox had in a slight degree lost, in Europe, its primitive intensity. The people who then existed proceeded from many generations which could, thanks to the process of selection, passably resist the epidemic. Individuals were not so readily affected as at the origin of the disease, or, if they had the disease, they succumbed to it in a smaller proportion; or, yet again, those who survived rarely contracted the disease a second time. It was supposed that those who had the disease by inoculation were sheltered from a repetition, and the dangerous practice of inoculation would not have continued, but for this opinion. Vaccination, then, came at an epoch when the European population found itself in ameliorated conditions with regard to epidemic small-pox. Practised with ardor, it had the effect to render small-pox very rare. But, precisely because it had become rare in the generation which immediately succeeded Jenner, in the generation which issued from that was found a majority composed of persons who had not been exposed to the epidemic. Among them must have been some persons who naturally, or by atavism, were disposed to take the infection. From that cause arose a certain renewed sensitiveness (recrudescence), which vaccination could less easily control.

In other words, after two or three vaccinated generations, the European population having been slightly exposed to the small-pox, found itself approximating to the conditions of a population in which the disease appears for the first time. The attack is not altogether so