Читать книгу Falling in Love; With Other Essays on More Exact Branches of Science - Allen Grant, Griffiths Arthur - Страница 6

For many generations past that problematical animal, the toad-in-a-hole (literal, not culinary) has been one of the most familiar and interesting personages of contemporary folk-lore and popular natural history. From time to time he turns up afresh, with his own wonted perennial vigour, on paper at least, in company with the great sea-serpent, the big gooseberry, the shower of frogs, the two-headed calf, and all the other common objects of the country or the seaside in the silly season. No extraordinary natural phenomenon on earth was ever better vouched for—in the fashion rendered familiar to us by the Tichborne claimant—that is to say, no other could ever get a larger number of unprejudiced witnesses to swear positively and unreservedly in its favour. Unfortunately, however, swearing alone no longer settles causes offhand, as if by show of hands, 'the Ayes have it,' after the fashion prevalent in the good old days when the whole Hundred used to testify that of its certain knowledge John Nokes did not commit such and such a murder; whereupon John Nokes was forthwith acquitted accordingly. Nowadays, both justice and science have become more exacting; they insist upon the unpleasant and discourteous habit of cross-examining their witnesses (as if they doubted them, forsooth!), instead of accepting the witnesses' own simple assertion that it's all right, and there's no need for making a fuss about it. Did you yourself see the block of stone in which the toad is said to have been found, before the toad himself was actually extracted? Did you examine it all round to make quite sure there was no hole, or crack, or passage in it anywhere? Did you satisfy yourself after the toad was released from his close quarters that no such hole, or crack, or passage had been dexterously closed up, with intent to deceive, by plaster, cement, or other artificial composition? Did you ever offer the workmen who found it a nominal reward—say five shillings—for the first perfectly unanswerable specimen of a genuine unadulterated antediluvian toad? Have you got the toad now present, and can you produce him here in court (on writ of habeas corpus or otherwise), together with all the fragments of the stone or tree from which he was extracted? These are the disagreeable, prying, inquisitorial, I may even say insulting, questions with which a modern man of science is ready to assail the truthful and reputable gentlemen who venture to assert their discovery, in these degenerate days, of the ancient and unsophisticated toad-in-a-hole.

Now, the worst of it is that the gentlemen in question, being unfamiliar with what is technically described as scientific methods of investigation, are very apt to lose their temper when thus cross-questioned, and to reply, after the fashion usually attributed to the female mind, with another question, whether the scientific person wishes to accuse them of downright lying. And as nothing on earth could be further from the scientific person's mind than such an imputation, he is usually fain in the end to give up the social pursuit of postprandial natural history (the subject generally crops up about the same time as the after-dinner coffee), and to let the prehistoric toad go on his own triumphant way, unheeded.

As a matter of fact, nobody ever makes larger allowances for other people, in the estimate of their veracity, than the scientific inquirer. Knowing himself, by painful experience, how extremely difficult a matter it is to make perfectly sure you have observed anything on earth quite correctly, and have eliminated all possible chances of error, he acquires the fixed habit of doubting about one-half of whatever his fellow-creatures tell him in ordinary conversation, without for a single moment venturing to suspect them of deliberate untruthfulness. Children and servants, if they find that anything they have been told is erroneous, immediately jump at the conclusion that the person who told them meant deliberately to deceive them; in their own simple and categorical fashion they answer plumply, 'That's a lie.' But the man of science is only too well acquainted in his own person with the exceeding difficulty of ever getting at the exact truth. He has spent hours of toil, himself, in watching and observing the behaviour of some plant, or animal, or gas, or metal; and after repeated experiments, carefully designed to exclude all possibility of mistake, so far as he can foresee it, he at last believes he has really settled some moot point, and triumphantly publishes his final conclusions in a scientific journal. Ten to one, the very next number of that same journal contains a dozen supercilious letters from a dozen learned and high-salaried professors, each pointing out a dozen distinct and separate precautions which the painstaking observer neglected to take, and any one of which would be quite sufficient to vitiate the whole body of his observations. There might have been germs in the tube in which he boiled the water (germs are very fashionable just at present); or some of the germs might have survived and rather enjoyed the boiling; or they might have adhered to the under surface of the cork; or the mixture might have been tampered with during the experimenter's temporary absence by his son, aged ten years (scientific observers have no right, apparently, to have sons of ten years old, except perhaps for purposes of psychological research); and so forth, ad infinitum. And the worst of it all is that the unhappy experimenter is bound himself to admit that every one of the objections is perfectly valid, and that he very likely never really saw what with perfect confidence he thought and said he had seen.

This being an unbelieving age, then, when even the book of Deuteronomy is 'critically examined,' let us see how much can really be said for and against our old friend, the toad-in-a-hole; and first let us begin with the antecedent probability, or otherwise, of any animal being able to live in a more or less torpid condition, without air or food, for any considerable period of time together.

A certain famous historical desert snail was brought from Egypt to England as a conchological specimen in the year 1846. This particular mollusk (the only one of his race, probably, who ever attained to individual distinction), at the time of his arrival in London, was really alive and vigorous; but as the authorities of the British Museum, to whose tender care he was consigned, were ignorant of this important fact in his economy, he was gummed, mouth downward, on to a piece of cardboard, and duly labelled and dated with scientific accuracy, 'Helix desertorum, March 25, 1846.' Being a snail of a retiring and contented disposition, however, accustomed to long droughts and corresponding naps in his native sand-wastes, our mollusk thereupon simply curled himself up into the topmost recesses of his own whorls, and went placidly to sleep in perfect contentment for an unlimited period. Every conchologist takes it for granted, of course, that the shells which he receives from foreign parts have had their inhabitants properly boiled and extracted before being exported; for it is only the mere outer shell or skeleton of the animal that we preserve in our cabinets, leaving the actual flesh and muscles of the creature himself to wither unobserved upon its native shores. At the British Museum the desert snail might have snoozed away his inglorious existence unsuspected, but for a happy accident which attracted public attention to his remarkable case in a most extraordinary manner. On March 7, 1850, nearly four years later, it was casually observed that the card on which he reposed was slightly discoloured; and this discovery led to the suspicion that perhaps a living animal might be temporarily immured within that papery tomb. The Museum authorities accordingly ordered our friend a warm bath (who shall say hereafter that science is unfeeling!), upon which the grateful snail, waking up at the touch of the familiar moisture, put his head cautiously out of his shell, walked up to the top of the basin, and began to take a cursory survey of British institutions with his four eye-bearing tentacles. So strange a recovery from a long torpid condition, only equalled by that of the Seven Sleepers of Ephesus, deserved an exceptional amount of scientific recognition. The desert snail at once awoke and found himself famous. Nay, he actually sat for his portrait to an eminent zoological artist, Mr. Waterhouse; and a woodcut from the sketch thus procured, with a history of his life and adventures, may be found even unto this day in Dr. Woodward's 'Manual of the Mollusca,' to witness if I lie.

I mention this curious instance first, because it is the best authenticated case on record (so far as my knowledge goes) of any animal existing in a state of suspended animation for any long period of time together. But there are other cases of encysted or immured animals which, though less striking as regards the length of time during which torpidity has been observed, are much more closely analogous to the real or mythical conditions of the toad-in-a-hole. That curious West African mud-fish, the Lepidosiren (familiar to all readers of evolutionary literature as one of the most singular existing links between fish and amphibians), lives among the shallow pools and broads of the Gambia, which are dried up during the greater part of the tropical summer. To provide against this annual contingency, the mud-fish retires into the soft clay at the bottom of the pools, where it forms itself a sort of nest, and there hibernates, or rather æstivates, for months together, in a torpid condition. The surrounding mud then hardens into a dry ball; and these balls are dug out of the soil of the rice-fields by the natives, with the fish inside them, by which means many specimens of lepidosiren have been sent alive to Europe, embedded in their natural covering. Here the strange fish is chiefly prized as a zoological curiosity for aquariums, because of its possessing gills and lungs together, to fit it for its double existence; but the unsophisticated West Africans grub it up on their own account as a delicacy, regardless of its claims to scientific consideration as the earliest known ancestor of all existing terrestrial animals. Now, the torpid state of the mud-fish in his hardened ball of clay closely resembles the real or supposed condition of the toad-in-a-hole; but with one important exception. The mud-fish leaves a small canal or pipe open in his cell at either end to admit the air for breathing, though he breathes (as I shall proceed to explain) in a very slight degree during his æstivation; whereas every proper toad-in-a-hole ought by all accounts to live entirely without either feeding or breathing in any way. However, this is a mere detail; and indeed, if toads-in-a-hole do really exist at all, we must in all probability ultimately admit that they breathe to some extent, though perhaps very slightly, during their long immurement.

And this leads us on to consider what in reality hibernation is. Everybody knows nowadays, I suppose, that there is a very close analogy between an animal and a steam-engine. Food is the fuel that makes the animal engine go; and this food acts almost exactly as coal does in the artificial machine. But coal alone will not drive an engine; a free draught of open air is also required in order to produce combustion. Just in like manner the food we eat cannot be utilised to drive our muscles and other organs unless it is supplied with oxygen from the air to burn it slowly inside our bodies. This oxygen is taken into the system, in all higher animals, by means of lungs or gills. Now, when we are working at all hard, we require a great deal of oxygen, as most of us have familiarly discovered (especially if we are somewhat stout) in the act of climbing hills or running to catch a train. But when we are doing very little work indeed, as in our sleeping hours, during which muscular movement is suspended, and only the general organic life continues, we breathe much more slowly and at longer intervals. However, there is this important difference (generally speaking) between an animal and a steam-engine. You can let the engine run short of coals and come to a dead standstill, without impairing its future possibilities of similar motion; you have only to get fresh coals, after weeks or months of inaction, and light up a fresh fire, when your engine will immediately begin to work again, exactly the same as before. But if an animal organism once fairly runs down, either from want of food or any other cause—in short, if it dies—it very seldom comes to life again.

I say 'very seldom' on purpose, because there are a few cases among the extreme lower animals where a water-haunting creature can be taken out of the water and can be thoroughly dried and desiccated, or even kept for an apparently unlimited period wrapped up in paper or on the slide of a microscope; and yet, the moment a drop of water is placed on top of it, it begins to move and live again exactly as before. This sort of thorough-going suspended animation is the kind we ought to expect from any well-constituted and proper-minded toad-in-a-hole. Whether anything like it ever really occurs in the higher ranks of animal life, however, is a different question; but there can be no doubt that to some slight extent a body to all intents and purposes quite dead (physically speaking) by long immersion in water—a drowned man, for example—may really be resuscitated by heat and stimulants, applied immediately, provided no part of the working organism has been seriously injured or decomposed. Such people may be said to be pro tem. functionally, though not structurally, dead. The heart has practically ceased to beat, the lungs have ceased to breathe, and physical life in the body is temporarily extinct. The fire, in short, has gone out. But if only it can be lighted again before any serious change in the system takes place, all may still go on precisely as of old.

Many animals, however, find it convenient to assume a state of less complete suspended animation during certain special periods of the year, according to the circumstances of their peculiar climate and mode of life. Among the very highest animals, the most familiar example of this sort of semi-torpidity is to be found among the bears and the dormice. The common European brown bear is a carnivore by descent, who has become a vegetarian in practice, though whether from conscientious scruples or mere practical considerations of expediency, does not appear. He feeds chiefly on roots, berries, fruits, vegetables, and honey, all of which he finds it comparatively difficult to procure during winter weather. Accordingly, as everyone knows, he eats immoderately in the summer season, till he has grown fat enough to supply bear's grease to all Christendom. Then he hunts himself out a hollow tree or rock-shelter, curls himself up quietly to sleep, and snores away the whole livelong winter. During this period of hibernation, the action of the heart is reduced to a minimum, and the bear breathes but very slowly. Still, he does breathe, and his heart does beat; and in performing those indispensable functions, all his store of accumulated fat is gradually used up, so that he wakes in spring as thin as a lath and as hungry as a hunter. The machine has been working at very low pressure all the winter: but it has been working for all that, and the continuity of its action has never once for a moment been interrupted. This is the central principle of all hibernation; it consists essentially of a very long and profound sleep, during which all muscular motion, except that of the heart and lungs, is completely suspended, while even these last are reduced to the very smallest amount compatible with the final restoration of full animal activity.

Thus, even among warm-blooded animals like the bears and dormice, hibernation actually occurs to a very considerable degree; but it is far more common and more complete among cold-blooded creatures, whose bodies do not need to be kept heated to the same degree, and with whom, accordingly, hibernation becomes almost a complete torpor, the breathing and the action of the heart being still further reduced to very nearly zero. Mollusks in particular, like oysters and mussels, lead very monotonous and uneventful lives, only varied as a rule by the welcome change of being cut out of their shells and eaten alive; and their powers of living without food under adverse circumstances are really very remarkable. Freshwater snails and mussels, in cold weather, bury themselves in the mud of ponds or rivers; and land-snails hide themselves in the ground or under moss and leaves. The heart then ceases perceptibly to beat, but respiration continues in a very faint degree. The common garden snail closes the mouth of his shell when he wants to hibernate, with a slimy covering; but he leaves a very small hole in it somewhere, so as to allow a little air to get in, and keep up his breathing to a slight amount. My experience has been, however, that a great many snails go to sleep in this way, and never wake up again. Either they get frozen to death, or else the respiration falls so low that it never picks itself up properly when spring returns. In warm climates, it is during the summer that mollusks and other mud-haunting creatures go to sleep; and when they get well plastered round with clay, they almost approach in tenacity of life the mildest recorded specimens of the toad-in-a-hole.

For example, take the following cases, which I extract, with needful simplifications, from Dr. Woodward.

'In June 1850, a living pond mussel, which had been more than a year out of water, was sent to Mr. Gray, from Australia. The big pond snails of the tropics have been found alive in logs of mahogany imported from Honduras; and M. Caillaud carried some from Egypt to Paris, packed in sawdust. Indeed, it isn't easy to ascertain the limit of their endurance; for Mr. Laidlay, having placed a number in a drawer for this very purpose, found them alive after five years' torpidity, although in the warm climate of Calcutta. The pretty snails called cyclostomas, which have a lid to their shells, are well known to survive imprisonments of many months; but in the ordinary open-mouthed land-snails such cases are even more remarkable. Several of the enormous tropical snails often used to decorate cottage mantelpieces, brought by Lieutenant Greaves from Valparaiso, revived after being packed, some for thirteen, others for twenty months. In 1849, Mr. Pickering received from Mr. Wollaston a basketful of Madeira snails (of twenty or thirty different kinds), three-fourths of which proved to be alive, after several months' confinement, including a sea voyage. Mr. Wollaston has himself recorded the fact that specimens of two Madeira snails survived a fast and imprisonment in pill-boxes of two years and a half duration, and that large numbers of a small species, brought to England at the same time, were all living after being inclosed in a dry bag for a year and a half.'

Whether the snails themselves liked their long deprivation of food and moisture we are not informed; their personal tastes and inclinations were very little consulted in the matter; but as they and their ancestors for many generations must have been accustomed to similar long fasts during tropical droughts, in all likelihood they did not much mind it.

The real question, then, about the historical toad-in-a-hole narrows itself down in the end merely to this—how long is it credible that a cold-blooded creature might sustain life in a torpid or hibernating condition, without food, and with a very small quantity of fresh air, supplied (let us say) from time to time through an almost imperceptible fissure? It is well known that reptiles and amphibians are particularly tenacious of life, and that some turtles in particular will live for months, or even for years, without tasting food. The common Greek tortoise, hawked on barrows about the streets of London and bought by a confiding British public under the mistaken impression that its chief fare consists of slugs and cockroaches (it is really far more likely to feed upon its purchaser's choicest seakale and asparagus), buries itself in the ground at the first approach of winter, and snoozes away five months of the year in a most comfortable and dignified torpidity. A snake at the Zoo has even been known to live eighteen months in a voluntary fast, refusing all the most tempting offers of birds and rabbits, merely out of pique at her forcible confinement in a strange cage. As this was a lady snake, however, it is possible that she only went on living out of feminine obstinacy, so that this case really counts for very little.

Toads themselves are well known to possess all the qualities of mind and body which go to make up the career of a successful and enduring anchorite. At the best of times they eat seldom and sparingly, while a forty days' fast, like Dr. Tanner's, would seem to them but an ordinary incident in their everyday existence. In the winter they hibernate by burying themselves in the mud, or by getting down cracks in the ground. It is also undoubtedly true that they creep into holes wherever they can find one, and that in these holes they lie torpid for a considerable period. On the other hand, there is every reason to believe that they cannot live for more than a certain fixed and relatively short time entirely without food or air. Dr. Buckland tried a number of experiments upon toads in this manner—experiments wholly unnecessary, considering the trivial nature of the point at issue—and his conclusion was that no toad could get beyond two years without feeding or breathing. There can be very little doubt that in this conclusion he was practically correct, and that the real fine old crusted antediluvian toad-in-a-hole is really a snare and a delusion.

That, however, does not wholly settle the question about such toads, because, even though they may not be all that their admirers claim for them, they may yet possess a very respectable antiquity of their own, and may be very far from the category of mere vulgar cheats and impostors. Because a toad is not as old as Methuselah, it need not follow that he may not be as old as Old Parr; because he does not date back to the Flood, it need not follow that he cannot remember Queen Elizabeth. There are some toads-in-a-hole, indeed, which, however we may account for the origin of their legend, are on the very face of it utterly incredible. For example, there is the favourite and immensely popular toad who was extracted from a perfectly closed hole in a marble mantelpiece. The implication of the legend clearly is that the toad was coeval with the marble. But marble is limestone, altered in texture by pressure and heat, till it has assumed a crystalline structure. In other words we are asked to believe that that toad lived through an amount of fiery heat sufficient to burn him up into fine powder, and yet remains to tell the tale. Such a toad as this obviously deserves no credit. His discoverers may have believed in him themselves, but they will hardly get other people to do so.

Still, there are a great many ways in which it is quite conceivable that toads might get into holes in rocks or trees so as to give rise to the common stories about them, and might even manage to live there for a considerable time with very small quantities of food or air. It must be remembered that from the very nature of the conditions the hole can never be properly examined and inspected until after it has been split open and the toad has been extracted from it. Now, if you split open a tree or a rock, and find a toad inside it, with a cavity which he exactly fills, it is extremely difficult to say whether there was or was not a fissure before you broke the thing to pieces with your hatchet or pickaxe. A very small fissure indeed would be quite sufficient to account for the whole delusion; for if the toad could get a little air to breathe slowly during his torpid period, and could find a few dead flies or worms among the water that trickled scantily into his hole, he could manage to drag out a peaceful and monotonous existence almost indefinitely. Here are a few possible cases, any one of which will quite suffice to give rise to at least as good a toad-in-the-hole as ninety-nine out of a hundred published instances.

An adult toad buries himself in the mud by a dry pond, and gets coated with a hard solid coat of sun-baked clay. His nodule is broken open with a spade, and the toad himself is found inside, almost exactly filling the space within the cavity. He has only been there for a few months at the outside; but the clay is as hard as a stone, and to the bucolic mind looks as if it might have been there ever since the Deluge. Good blue lias clay, which dries as solid as limestone, would perform this trick to perfection; and the toad might easily be relegated accordingly to the secondary ages of geology. Observe, however, that the actual toads so found are not the geological toads we should naturally expect under such remarkable circumstances, but the common everyday toads of modern England. This shows a want of accurate scientific knowledge on the part of the toads which is truly lamentable. A toad who really wished to qualify himself for the post ought at least to avoid presenting himself before a critical eye in the foolish guise of an embodied anachronism. He reminds one of the Roman mother in a popular burlesque, who suspects her son of smoking, and vehemently declares that she smells tobacco, but, after a moment, recollects the historical proprieties, and mutters to herself, apologetically, 'No, not tobacco; that's not yet invented.' A would-be silurian or triassic toad ought, in like manner, to remember that in the ages to whose honours he aspires his own amphibian kind was not yet developed. He ought rather to come out in the character of a ceratodus or a labyrinthodon.