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very different from those to which we have been in the habit hitherto of applying the formula, "omne vivum ex ovo." There remains, it is true, the ground of contagion. Some observers admit that no ovules exist in the air, or in the water, as a constant fact; but they say that ovules may exist around bodies already infected; and because several parasites are contagious, they would view all heterogeny as the fact of a contagion. This opinion is shown to be unacceptable by the generation of infusoria; for when a fermentescible body is taken, detaching it from a living body; and when it is immediately enclosed in apparatus where only distilled water and artificial air enter, it is impossible to suppose any contagion whatever. That it might take place in certain cases, exceptionally, is all that it is possible to admit, after what we have related in the preceding article against the dissemination of ovules.

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The same for parasites: their contagion is not contestable not contested, in certain cases, for the itch, pediculi, the pulex, the myceliums. But who would dare maintain that lumbrici, tænias, cysticerques, gourd-worms, the oxyurus, the trigonocephalus, are only developed by contagion? And even for species eminently contagious, this origin is often inadmissible; there are cases where these parasites-pediculi, for example-develop themselves outside of all possible communication; children, either in the beginning or at the end of a malady, may be suddenly covered with this vermin, without any contagion being possible. Finally, contagion itself explains nothing; for even the itch can not be taken at pleasure. Many persons expose themselves with impunity to the contagion, which only takes on condition of a peculiar morbid predisposition: so that this contagion is not itself the malady, but the occasional cause of the malady. If the malady be developed, the parasite will develop itself and multiply; if not, it perishes barren. In the last researches made upon the itch by M. Bourguignon, who has long been occupied with this question, it is demonstrated that the acarus scarabei contains a venomous juice, which is by itself capable of producing vesicles, in every respect resembling those produced by the insect itself; so that it would seem to result that the acarus only develops on condition of having given rise to a vesicle, and to the production of the vesicular liquid which is to nourish it; thus it develops a lesion, in order to feed upon the morbid product. But if the indi

vidual exposed to contagion resist the morbid production, by the very fact that the disease does not take place, the acarus perishes sterile. Contagion is, then, insufficient to explain all the cases of heterogeny; and the reason of this phenomenon does not lie in the exterior causes, but in the very disposition of the fermentescible body, or heterogenic blastema.

Under whatever point of view we examine this question of the preexistence of ovules in the fermentescible body, the result is still the same. This body contains no visible ovules; none can come to it from the air, or from water which contains none; we can not suppose that it has received by the generation of the being all which would be necessary to the development of its parasites and of infusories; the theory of metamorphoses explains nothing on this point; and finally, contagion has hardly a greater value. In short, heterogeny can not be explained by the preëxistence of ovules.

2. Does heterogeny depend simply upon material dispositions or molecular arrangements? We have shown that heterogeny is manifested in no purely material or inorganic body, and that it is only observed in blastemas which are still organized; all experiments agree on this point. It is not, then, matter itself which gives rise to heterogeny, but bodies which still contain something of the living forces which have animated them.

Parts detached from a living body do not immediately lose all vital force; but only gradually do they enter by decomposition the empire of purely physical and chemical forces. On a limb which has just been amputated, we find signs of contractility and of irritability; and these phenomena last several hours longer. It is known that a membrane, even when dried, preserves, as long as it is not altered in its nature, the endosmotic property which it possessed in the fresh state, and during life. The contractility of the vibratile cilia persists on the epithelial cells which have been for many hours torn away from the nasal fossæ. Zoösperms preserve, several hours after they have been emitted, their lively and rapid movements. The yellow elastic tissue keeps long after death its properties, so long as the alteration of the tissue is not effected. In a word, all the forces called organic, may remain for a certain length of time inherent to the organized body separated from the living organism to which it belonged.

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Forces, called by the Germans plastic, those which combine matter, remain much longer after the manifestations of animal life

have ceased; dead parts which have long lost their organic forces, still keep their plastic forces which hold them in their organized arrangement. It is to their persistence that we justly attribute the properties which these organized bodies manifest, long after the separation of parts from the living whole. Thus diastase and pepsine preserve during indefinite periods, so long as they are not decomposed, their fermentescible virtues. The animal viruses, in another order of forces, are but organic matter, which, so long as it is not altered chemically, preserves virtues which it has acquired during life; and these venoms are preserved for very long periods after the death of the animal. The same is true of the vaccine virus, of variolic pus, of chancrous pus, etc., which are but organic matter containing virtues acquired during life.

3. The two heterogenic blastemas that of infusoria and that of parasites are both, we have just seen, matter which conceals forces, pathological matter as well as the fermentescible body of infusories. And it is not as chemical matter that these blastemas are generated; it is as organic matter treasuring powers of activity. There are genesic powers, or, if another expression be preferred, seminal virtues, independent of the material forms of seeds or eggs.

We have seen that the same matter gives, according to particular arrangements, different products. This is especially sensible for parasitic productions. I will not say that the blastema which gives rise to the acarus scabiei, that of the pediculi, that of myceliums, of tænias, of cysticerques, of ascarides, and all the other parasites, are in all cases identically the same, chemically speaking, although no chemical differences have ever been appreciated. But these differences, if they exist, are doubtless very slight; and it is very probable that they are of no value, in the heterogenic point of view, since we can detect no chemical differences between ordinary variolic vaccine pus, chancrous pus, and pus pus, pus, in which vibrios are formed.

It is not because the blastemas differ under the chemical point of view that they give rise to different parasitic products, but rather because, with different morbid dispositions, and according to the malady with which the individual is attacked, there is produced in the same liquids or solids of the organism sometimes a cysticerque, sometimes an echinococcus, sometimes another parasite.

So of the generation of infusories from the fermentescible body. "A certain coleopter, a certain spider, a certain lepidopter, has

each at its death a cryptogamic vegetation that takes possession of it," justly remarks M. Pouchet; and he adds, that "such examples are extremely numerous." Now, each of these bodies is not confined to the production of a single kind of infusions; it may, on the contrary, produce many species,-sometimes one, sometimes another, sometimes several at once, according to dispositions as yet little known. Thus in two experiments of M. Pouchet, the same matter employed, a little wisp of hay, once produced aspergilli, another time the penicillium glaucum; and in two experiments of M. Montegazza, the same matter, an infusion of lettuce, gave rise once to monads, another time to bacterium sermo. There appear to be, then, dispositions independent of the appreciable material composition, and which seem to act in the same way as in the production of parasites. The difference in the two cases depends only upon the position of the fermentescible body : in one, this body is distracted and completely separated from the living support such is the blastema of infusories; in the other, this blastema still holds to a living support - such is the parasitic blastema. And remarkable facts show that this difference may be sometimes unimportant; thus when vibrios are developed in pus within the living organism, or when pediculi suddenly show themselves upon a corpse already several hours dead. There is then a

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very curious relation to be observed between infuscries and parasites the latter are developed in consequence of morbid dispositions during life, and the former proceed from dispositions certainly analogous, but after death; while here and there an exception interlocks the phenomena completely as either encroaches upon the field of the other.

These generations are not given up to chance; and there are not as many different beings as there are occasions for their generation; on the contrary, these abnormal generations, these parasites, and these infusories, have their species; these species are known, they are described, they are classed, and they are always found again the same; they have their definite types, so that the generative causes which produce them are not promiscuous heterogenic causes, but specific causes, which act as true germs. The ovule, it is true, is wanting; it is seen no where; it can not be materially seized; we can not even understand how it should materially subsist, without alteration, through all the phenomena of life into which it would pass if it existed; but its seminal power is clearly manifested.

Parasites, like maladies, are hereditary. Some attacks everybody; and few children, exposed to lice, escape this contagion. Some are peculiar to races or to families; the dragunculus is observed among the race that inhabits Arabia and the neighboring African coasts; the tænia among the Swiss, and in Germany; the botriocephalus on the other side of the Vistula.

Among the parasites which are hereditary in our country, there are none more remarkable than the oxyurus vermicularis, which sometimes skips a generation, is transmitted from the grandfather to the grandson, and is developed in the son at the very age when it was developed in the father, or in the ancestor. In order to explain these facts, hereditary dispositions must indeed be admitted. To admit hereditary ovules, is the wildness of an unrestrained hypothesis; to admit hereditary aptitudes for production, is implicitly to accept the doctrine of seminal virtues.

For infusories as for parasites, the facts are the same. Every living species produces at its death a certain number of infusory species, and always the same, as during life it can produce a certain number of parasitic species, always the same. Every species has its infusories after death, as it has its parasites during life; and both these aptitudes must be transmitted by generation, along with so many other impressions from parents to children, influencing their development, their acts, the formation of their tissues, and all the phenomena of life.

The essential principle exists alone as such; but the form of its action may vary according to the modifications which it undergoes by the contact of final causes; and hence the so great variations of its acts. Thus maladies have no subsisting active principleno morbid force; maladies are but the morbid modifications of the normal energy. They are hereditary, and the aptitude to develop them is transmitted from father to son; they are only predispositions passed into acts; and as they have no subsisting principle, they are but intentional forms transmitted by generation."

On the day when Man became susceptible of illness, he became equally susceptible of producing beings of corruption and of imperfection-beings of destruction; and these predispositions, transmitted from generation to generation, exist in him as the intentional forms which his vegetative or formative energy can endue.

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