Notes on Collecting and Preserving Natural-History Objects. VariousЧитать онлайн книгу.
We have passed some of the very happiest moments of our lives in solitary quarries, or on green hill-sides,
"The world forgetting, by the world forgot!"
There, amid the wreck of former creations, and with the glory of the present one around us, we have yielded to the delicious sense of reverie, such as can only be begotten under such circumstances. The shady side of the quarry has screened us from solar heat, and, whilst the air has been melodious with a thousand voices, we have made personal acquaintance with the numerous objects of God's creation, animals and plants. How apt are the thoughts of the poet Crabbe, and how well do they convey the feeling of the young geologist in such places:
"It is a lonely place, and at the side
Rises a mountain rock in rugged pride;
And in that rock are shapes of shells, and forms
Of creatures in old worlds, and nameless worms;
Whole generations lived and died, ere man,
A worm of other class, to crawl began."
II.
BONES.
By Edward Fentone Elwin, Caius College.
Why is it that the students of Osteology are so few in number? It is a branch of science which offers a wide field for original research, and one in which at every step one's interest must get more and more engrossed. It is a branch of science in which a sufficient portion of its elements may be rapidly learned, in order to set the student fairly on his road. The barriers which surround it are few: that is to say, the technical barriers are few. Many people who want to occupy themselves with scientific study are deterred, because of the feeling that there are so many laborious preliminaries to be gone through before they can begin to take any real pleasure in the pursuit. Now, in Osteology it is true that a wide and really almost unexplored field lies open before one, but the equipments necessary to fit one for one's journey are easily attained. The first step is to get thoroughly acquainted with some one typical specimen, as a standard of comparison for all future work. It matters little what species is taken; whichever comes most convenient. Some familiar mammal of fair size is the best. The dog is as good as any, and easy to obtain. There ought never to be any real difficulty in getting a suitable specimen. If expense is no object, the simplest way is to get a preparation, set up so as readily to take to pieces, at any of the bone-preservers' shops in London. One like this costs only a moderate sum, and is, of course, the least trouble, although the manner in which professionals prepare their bones is not altogether satisfactory. But we may regard this as something in the light of a luxury; and it is not hard to prepare one's own specimens, provided we do not mind a little manipulation with unsavoury objects. I have given hints as to the best method by which this may be done in various pages of 'Science-Gossip.'[A] Of course, as one's work gets on, one needs further specimens, but I do not think that anyone who keeps his eyes open need be at a loss in this matter. I have picked up several admirable bones ready cleaned by the wind and weather, and many slightly damaged ones may be got at naturalists' shops for small sums, which are almost as good as the perfect ones for an observer's purposes. Even single and isolated bones are often very instructive.
[A] 'Science-Gossip' for 1873, p. 39; for 1874, p. 226.
But the first main point is that of getting the forms, peculiarities, names, and positions of the bones of one skeleton fully impressed on the student's mind. As to the books which are to help him to do this, it is very hard to know what to recommend. As far as I know, there is no really luminous book on osteology in existence. So far as learning the names and peculiarities of the bones, nothing could be better or more to the purpose than Flower's 'Osteology of the Mammalia'; but this treats only of one class, and does not get beyond technical description. The first and second volumes of Owen's 'Comparative Anatomy of Vertebrates' fill the gap the best of any, and yet these are by no means what we really want. There is a good deal about bones in Huxley's 'Anatomy of Vertebrated Animals,' but in such a fragmentary and scattered form as to be of little use. The fact is, the field is yet open for an Osteological Manual. Much has been written on the subject. Pages of precise and accurate description, beautiful and artistic sheets of plates of bones without number, can be seen in any scientific library. But this is only half the matter. We want to advance a step farther. It is the relation between structure and function which needs working out.
When a new bone finds its way into the student's hands, he observes some peculiarity in shape or structure in which it differs from the bones he is already acquainted with; the question naturally occurs to him, Why does this bone assume one shape in one animal, and in another is modified into a different form? He may look in vain in his books for an answer to his query. And yet it is points like these which, in my opinion, make up the true science of Osteology. It is through careful, constant, and intelligent observation, that these enigmas are to be solved. Observation, indoors and out; close attention to the habits of the animal in question, on the one hand, and careful consideration of its anatomical peculiarities, on the other.
Let me give an instance of this, first of all taking it as an axiom that everything has been done with a purpose. Take, then, the skull of a crocodile. What do we find? The orbits of the eyes, the nasal orifice, the passages leading to the auditory apparatus, all situated on a plane, along the upper flattened surface of the head. What, then, is the cause of this? Palpably to allow the crocodile to remain submerged in the water, with its nose, eyes, and ears just above the surface to warn him of the approach of enemies or prey, and the rest of his carcase securely hidden beneath the waters.
Take another instance. Observe the habits of a mole. With what rapidity it burrows underground, shovelling away the earth with its fore feet. Then look at its skeleton. We find just what we should have expected. The bones of its fore legs of astounding strength and breadth, furnished with deep grooves, which, together with its sternum or breastbone, which is furnished with a keel almost like that of the sternum of a bird, afford attachment to the powerful muscles. Its hind legs, being simply needed for locomotion, are of the normal size. So, also, with the birds. The size of the keel of the sternum varies in proportion to the powers of flight which each species requires, for it is to the broad surfaces of the sternum that the great wing-muscles are attached. Take the skeleton of a hummingbird, which spends its life almost upon the wing. We find there a keel of so vast a size, that the remainder of the skeleton is reduced to insignificance in comparison. Of course, these instances that I have given are all of the most obvious nature, but they serve to show my meaning; and the same line of reasoning can, I am sure, be extended to all the more minute points in osteological structure.
In these researches, one is soon struck by the fact that in the modifications in various bones, or sets of bones, in accordance with the habits of each animal, the original type is never departed from, only modified. See, for example, the paddle of a whale. More like the fin of a fish in general appearance, and yet the same set of bones which are found in the arm of a man, are again found in an adapted form in the paddle of the whale. So, also, the fore leg of a horse preserves the same general plan. What is generally called its knee is in reality its wrist. It is there that we find the little group of bones which forms the carpus. All below it answers to our hand—a hand consisting of one finger.
Take even a wider instance. Compare the arm of a man and the wing of a bird. Still greater adaptations have taken place, and yet the plan remains the same. We still find the clavicle or collar-bone, the scapula or shoulder-blade, the humerus, ulna, and radius, answering to the same bones of our arm, a small carpus or wrist, and finally the phalanges or fingers, simplified and lengthened and anchylosed to form but one series of bone, with the exception of a rudimentary thumb. It is not uncommon to find a rudimentary bone like this which in some allied species is fully developed. The leg of the horse again gives us a very striking example of this. There is, so to speak, only a single finger, but we find, one on each side of this single finger, two small bones, commonly known only as splint-bones. These are the rudimentary traces of the same finger-bones, which in the rhinoceros are fully developed.
Now Osteology abounds