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(observes Professor Lindley) “the surface of stones constantly moistened by water, the glass of hot-houses, the face of rocks in the sea, or of walls where the sun never shines, or the hard paths in damp parts of gardens, after rain, cannot fail to have remarked a green mucous slime with which such places are covered; and which consists of algals in their simplest state of organization.” “ This slime” (says Bory de St. Vincent) “resembles a layer of albumen spread with a brush; it exfoliates in drying, and finally becomes visible by the manner in which it colours green or deep brown. One might call it a provisional creation, waiting to be organized, and then assuming different forms, according to the nature of the corpuscules which penetrate it or develop among it. It may further be said to be the origin of two very distinct existences, the one certainly animal, the other purely vegetable.* Here, it will be observed, that Bory de St. Vincent recognises, in these minute particles, "two very distinct existences ;” nor does he adduce any evidence to show that the vegetable corpuscules give rise to the animal development, or that the animal corpuscules give rise to the vegetable development of organization. A curious observation has been made respecting the motion of some minute species of plants-many of the conferva tribe (especially of the genera conferva ulvas and their near allies) produce, in their tubular threads, reproductive bodies or spores, which, after a time, acquire a power of rapid and quasi-voluntary motion while in the inside of their mother; by degrees, and in consequence of their tapping against the soft side of the cell that holds them, they escape into the water ; when there they swim about actively, just like animalculi, and at last, retreating to a shady place, attach themselves to a stone or some other body, lose their locomotion, and thenceforward germinate and grow like plants. This, when we reflect upon it, is not more marvellous than the dispersion of the reproductive seeds of vegetables by the wind upon land, which float hither and thither, with the “ down upon the thistle's beard,” until they find a congenial soil upon which they fix their habitat. Observation teaches us that all nature teems with life—the air we breathe, the dust upon which we tread, the water with which we slake our thirst, we find, when microscopically examined, loaded with animalculi, and germs, and ova, which rapidly develop into minute beings, curiously organized, and which apparently spring spontaneously into existence. The fact, however, of spontaneous generation has not yet been proved ; and in those experiments which pretend to exhibit the development of animalculi in solutions subjected to electrical action, there can be no doubt but their ova pre-existed in the fluid. "In my observations,” says Ehrenberg, who may be esteemed the Lindley's Vegetable Kingdom, vol. i. pp. 14, 15, et seq.
highest authority on this subject, "pursued with so much zeal for twelve years, I never witnessed the spontaneous origin of one infusorium from slime or vegetable tissue; and, supported by such experience, I am of opinion, that these animals are never formed by generatio primitiva, but originate from eggs. The active motions and contractions in plants and their parts, especially alge, ought not to give rise to the supposition of an animal nature, even when they are called infusorial, or animal motions. Internal nutritive organs, and a definite oval aperture for the reception of solid substances, which may be demonstrated, distinguish the apparently most simple animals from plants. I have never seen, in my numerous experiments, the motive algæ seeds take up the smallest quantity of solid nutriment; and thus the fruit-strewing algæ may be distinguished from the monads which swarm around it, in the same manner as the tree from a bird.”
When we leave the microscopic world, and approach other conditions of organization which exhibit little or no complexity of structure—as, for example, when we examine an hydatid or a polypus, or the gelatinous-looking body of the star-fish or the sea-urchinwe again recognise the existence of life in very simple structures, structures so simple as to militate against the idea of life being the result of any complex mechanical or chemical process. In animals, however, which are more highly organized, which possess a complicated nervous, circulating, respiratory, and digestive apparatus, the functions of which are implicated with and modified by certain chemical changes that occur in the ingesta and egesta, and also in the solids and fluids of the system itself—the sources whence life might have originated may, so to speak, appear theoretically multiplied. An infinitely more complicated organization is placed before the theorist who may imagine either that the mechanical action of the integral parts of the orgasm in a fatal state accounts for the development of life; or that certain affinities, in the gradual formation of the tissues, have, by virtue of electro-chemical action, developed life; or, entertaining mystical notions respecting material and spiritual agency, he may refer the principle of life to the soul itself. Thus the complexity of the structure of the higher order of animals has led to a great variety of hypotheses; but if we confine ourselves to the simplest organic condition under which life manifests itself, we discover no complicated structure which can suggest either a mechanical, chemical, or psychical cause for its developments.
Accordingly, our own observations and reflections induce us to believe in the existence of a principle of life (and we know no better word to designate our meaning) independent of these various organic condi
* Ehrenberg on the Origin of Organic Matter, from Simple Perceptible Matter, upud Taylor's Collection of Foreign Scientific Memoirs, vol. i. p. 566.
tions, and antecedent to all structure, being itself creative, and presiding over the formation and determining the rudimentary development of all beings; and we furthermore believe, that this principle of life, by its own determinate laws, preserves, in the process of organization, the definite form of different species, of animals and plants. Hence arises the uniformity of type observable in the animal creation ; hence the unity of organization observed by Blumenbach, upon which he founded his doctrine of the nisus formativus. We cannot, indeed, better explain our meaning than by citing the words of Geoffrey St. Hilaire, who fully recognised the facts, although not the theory we now advocate:-"Par cette expression" (the principle of life to which we apply these words, but which Geoffrey St. Hilaire applied to the nisus formativus of Blumenbach)“ on comprend les efforts ou la tendance de l'organization pour se développer, d'une seule et même manière, pour donner les résultats que nous disons ceux de la règle pour faire réapparoitre des produits qui répètent exactement les formes des anciennes races. Hence, when life is transmitted from parent to offspring, the ovum having received the principle of life which is initiative to the change of its condition, begins gradually to develop a new form, which ends in the organization of another individualism. The constant tendency of the vital laws to preserve uniformity of type becomes very remarkable in certain animals which do not require some organs which are common to their species, and which organs, therefore, do not advance in their development, but are left in a rudimentary state. The whale in embryo possesses the rudiments of teeth, but these not being required, the soft fan-like baleen appears in their stead. So also certain organs, the functions of which are required in one sex and not in the other, are fully developed only in the one which needs them, but stop short and remain in a rudimentary state in the other. In marsupial animals (the kangaroo) the female of the tribe has a process of bone proceeding from the pubes to support the pouch; but the male marsupial having no pouch, the bone appears only imperfectly developed. In the human race the mammæ are necessary for the female to nourish her offspring ; but the type is preserved—they exist in a rudimentary state also in the male. We cannot conceive this unity of type to exist unless we ascribe to the principle of life certain determinate laws which modify the development of organization.
All the phenomena of life with which we are conversant support this view; thus, the principle of life being independent of the organic structure in which it exists, requires certain external conditions—such as the presence of light, moisture, and a given temperature for its development.
Mems, du Muséum d'Histoire Naturelle, 9e année, p. 203.
The vitality of vegetable seeds, and the eggs of animals, will remain latent for an indefinite period. We are informed by Professor Lindley that he has raised three raspberry plants from seeds taken out of the stomach of a man whose skeleton was found in a barrow near Dorchester, thirty feet below the surface of the earth. His body had been buried with some coins of the Emperor Hadrian, and there could be no doubt but that the seeds were 1600 or 1700
There are many instances of the germination of grains of wheat found enclosed in the wrappers of Egyptian mummies. The desiccation of insects will also suspend for years the manifestation of life. The microscopic wheel animal, and the eel (vibrio tritici), which causes the ear cockle in wheat, will continue for twenty or thirty years in a dry and apparently dead state, but exposure to air and moisture quickly revives them. The most simple infusoria and rotaria become torpid upon being deprived of moisture; so also will the common garden snail, if put in a dry place, but it immediately revives upon application of moisture. The phenomenon of hybernation is also directly connected with the principle of life; it is indeed observed in those animals which become torpid during the winter season, that when the sensibility of all the functions is lessened, -the temperature lowered, the circulation slower, respiration imperceptible, and digestion suspended, vitality becomes more tenacious than ever under these physical abnormal conditions.* Fish and cold blooded animals survive an intense torpidity: “ The fish froze," says Captain Franklin, as fast as they were taken out of the nets, and in a short time became a solid mass of ice, and by a blow or two of the hatchet were easily split open, when the intestines might be removed in a lump, and if in this completely frozen state they were thawed before the fire, they recovered their animation.” The persistency of vitality, even after mutilation of the body, is in most of the cold blooded animals remarkable, and the restoration of lost parts opens before us a still wider field for observation.
Here also we may refer to a curious fact observed by physicians—viz., the transference of vitality which appears to take place when young persons are habitually placed in contact with the aged. This is not a nursery fiction. It is well attested by very competent authorities. “A not uncommon cause," observes Dr. James Copland, “ of depressed vital power is the young sleeping with the aged. This fact, however explained, has been long remarked, and is well known to every unprejudiced observer. I have on several occasions met with the counterpart of the following case — I was, a few years ago, consulted about a pale sickly, and thin boy, of about four or five years of age. He appeared to have no specific ailment, but there was a slow and remarkable decline of flesh and strength, and of the energy of the functions—what his mother very aptly termed a gradual blight. After inquiry into the history of the case, it came out that he had been a very robust and plethoric child up to his third year, when his grandmother, a very aged person, took him to sleep with her ; that he soon afterwards lost his good looks, and that he had continued to decline progressively ever since, notwithstanding medical treatment. I directed him to sleep apart from the aged parent, and prescribed gentle tonics, change of air, &c. The recovery was rapid; but it is not in children only that debility is induced by this mode of abstracting vital power. Young females married to very old men suffer in a similar manner, although seldom to so great an extent; and instances have come to my knowledge where they have suspected the cause of their debilitated state. These facts are often well known to the aged themselves, who consider the indulgence favourable to longevity, and thereby illustrate the selfishness which, in some persons, increases with their years.'
* Elliotson's Human Physiology, p. 698.
"* Every medical practitioner is well aware of the fact, and parents generally are advised not to allow their infants to sleep with aged persons. Now, it is evident, that if this emaciation arise from the abstraction of the vital power, as Dr. Copland expresses it, the principle of vitality must have an independent existence. But here the question suggests itself, where—supposing this view of the theory of life to be adopted-shall we expect to find the seat of the vital principle? The answer to us is obvious. We should expect to find it diffused throughout every organ and every tissue and distant part of the body, sustaining with unity of effect the functions of all the different organs for the support of the entire system. And were we pressed still further to hazard a speculation as to the material medium through which it becomes so diffused, we should be inclined, both from physiological and pathological evidence, to adopt, with certain modifications, the Hunterian hypothesis, —that the blood is its ostensible site, and vehicle ; in confirmation of which opinion it may be observed, that those tissues possess the highest vitality which are endowed with the highest vascularity; and those tissues which are the least vascular exhibit the lowest signs of vitality, such as the appendages to the dermoid system, the hair, nails, &e. Hence, also, if the supply of blood to any part be cut off by ligature, that part loses its vitality, and recovers it again when the circulation is restored.
We have thus seen that the principle of life opposes an active resistance (as is stated in the definition of Bichat) to those physical causes which may tend to disturb or destroy organic functions, and
Dictionary of Practical Medicine. By James Copland, M.D., F.R.S. Article " Debility," vol. i. p. 75.