CHAPTER XVI

Chapter 174,041 wordsPublic domain

HOW ZOOLOGISTS DO THEIR WORK

It is one of the most well-worn of commonplace sayings, that "one half the world does not know how the other half lives." It is equally true that one half the world does not know how the other half works; and especially is this the case when one of the world's halves is its learned, and the other its unlearned, half. The average business man probably has an idea that the man of learning has a pretty easy time of it, and that his most arduous occupation is to enlighten an attentive world by reading papers at the meetings of the British Association and the Royal Society. He has a vague idea that the man of learning sometimes uses midnight oil, but it would surprise him to be informed that the man of learning often sets to work at five o'clock in the morning--as is actually the case. And well he may, considering the magnitude of the task he has in hand, and the variety of the odds and ends of labour that it includes.

_Firstly_, how does he obtain the raw material for his work? The scientist, like the cook, must "first catch his hare" before any further details of work can be arranged. He does not, as a rule, do this in person, except when an animal of unusual interest is concerned. An army of collectors, all the world over, are constantly busy in searching for material for the zoologists, on land and sea. They look for employment and pay to the museums and laboratories of the learned world. When the specimens arrive, what is to be done with them? Some arrive alive, and may be dismissed from present consideration. The dead specimens give employment to a number of workers who are under the command of the man of learning. There are skins to be mounted and stuffed, bones to be articulated and set up, each practically the work of a different trade. There are drawings to be made of all important specimens, a task which affords employment for the artist and the photographer. There are carcases large and small, to be immersed in preservative fluids until they can be thoroughly examined in detail. And woe betide the zoologist who allows any of these tasks to be performed without his own personal supervision. He will realise, as all careless masters do, that blunders may be made in an hour, which cannot be repaired in a day. But when all is done that servants and helpers can accomplish, the real business remains to be done. Is there among the specimens one which has not been thoroughly overhauled by other writers, one whose every detail of structure is not already to be found printed in a book? That one must be examined with the utmost accuracy. If it is big enough, it must be dissected, and every part recorded and figured in diagrams. But suppose it is a small creature, whose parts can only be seen under the microscope, a long series of processes are necessary before it is ready for use. In its fresh state, it contains a quantity of water, and if left to itself would shortly decompose. Even if already immersed during carriage in various preservative fluids, it still contains much water, and, if so, neither will it keep for an indefinite length of time, nor could it be satisfactorily examined under the microscope. It must be soaked in one of various chemical solutions, to harden and preserve it. If very small indeed, a mere speck, it perhaps only needs to be transferred to a fluid in which it can be "mounted" and placed under the microscope. But with the vast majority of specimens, an immense amount of labour is needed before they are ready for inspection under the microscope.

This will easily be understood if we reflect for a moment on the way in which objects are examined under the microscope. For purposes of scientific investigation, they are rarely looked at under light that falls upon their surfaces, that is to say, by reflected light; for this method can show nothing but details which are external and comparatively unimportant. They are seen by light placed behind them so as to shine through them, _i.e._ by transmitted light. If the object is not extremely thin, it will shut out too much light, and thus it cannot be clearly seen, therefore all objects, except the most minute, must be divided into thin slices, technically known as "sections."

If we want to know not only the microscopic structure of organs, but also their shape and position in the body, and their relations with other parts, we must have every successive section carefully preserved, and the whole row arranged in correct successive order; the physiologist may often content himself with single sections; the zoologist must have rows and rows of them. What a task this was, a quarter of a century ago, for scientists who cut their sections by hand!

Let us, however, describe first the way in which objects are prepared for section-cutting--whether by hand or by machine. It has already been noticed that animal substances contain a quantity of water, and therefore will not keep. The same circumstance renders them soft and squashy, so that the sharpest razor in the world, in cutting a section, must necessarily do more or less damage to the structure of the delicate tissues. The water is held in the meshes of the tissues just as it is held, for example, in the meshes of a sponge. Now, if we were dealing with the sponge, we could get it to absorb any other fluid substance besides water; we might choose one that would prevent decomposition; we might choose one that would go harder by cooling; so as to change the sponge into a strong solid block that could be knocked about without sustaining any damage. This is exactly what we must do with our animal tissue to prepare it for section-cutting; and the most convenient fluid for the purpose is melted wax. But whereas we might take our sponge out of water, squeeze it dry, and dip it straight into melted wax, we can by no means do so with our animal tissues. For one thing they usually cannot be squeezed, and where they can, they would of course be irretrievably ruined by such a rough process. Even the transference of the specimen from one fluid to another of very different qualities and density, would deface the tissues. Cells would burst, or be squeezed out of shape, and organs would be loosed from their right position by the currents set up in all parts of the specimen, under such circumstances. We must, therefore, try to get rid of the water by degrees. This may be done by gradually adding alcohol, a fluid which may be diluted with water in any proportion. We begin with a comparatively weak solution of alcohol, say about fifty per cent., and immerse the specimen in this for some little time. The time required depends somewhat upon the size of the specimen; if a large one, a new fluid will take longer to filter through it. Then we must change this solution of alcohol for stronger ones, say seventy per cent. and ninety per cent. successively, and finally to absolute alcohol. By this time the alcohol will have removed almost nearly all trace of water from the specimen. The latter is now nearly but not quite ready to be imbedded in melted wax; but first we must soak it for a while in a fluid intermediate in thickness between the alcohol and the wax, and capable of mixing in a friendly manner with both. Then it goes into a bath of melted wax, and is kept for hours at a stated temperature until the wax permeates it thoroughly. Then the melted wax and the specimen along with it is poured into a little mould and left to cool. The block of wax containing the specimen is cut down to a quadrangular shape, and is now ready for section cutting. In old days the block was placed in a stand, and successive sections were cut from it by hand with a razor. But this process is much too slow for modern days. Machines called microtomes (_i.e._ cutters of small parts) have been invented, and of these there are several kinds--in all, however, the razor is worked by machine and not by hand, so as to secure steadiness and a uniform thinness of the sections. The old microtomes threw off each section separately; but now matters are so arranged that the wax of each section adheres to that of the next, and the whole series of sections forms a continuous ribbon of thin wax. A large specimen, affording a number of sections, thus results in a ribbon of considerable length. Further processes are now required to fit the sections for the microscope. The ribbon must be divided into successive pieces of a length determined by that of the slides to be used. These are mounted in order on the slides, steps are taken to melt away the wax from the sections, the latter are covered with Canada Balsam surmounted by a glass cover slip, and left for some time to dry. After this they are ready for examination, and it is only now that the work really begins. All that has gone before is mere handicraft; it is time now for science to be called into play.

The sections must be compared with others of the same kind which have been cut before. Do they entirely resemble these, or is there a difference somewhere? Happy the man who finds that his sections represent a fresh stage, perhaps older or younger than any that has been seen before in the history of the particular animal which is under investigation. Happier still the man who has succeeded in getting hold of an animal which has not been described before. He will make haste to write a full description of it, illustrated by drawings; to found a new theory on it, if that can possibly be done; and to publish it to the world. It will go all over the globe. To every country in Europe; to the centres of learning in the United States; to universities in New Zealand and Australia, and our other colonies; and perhaps even to "Far Japan."

When in his turn he receives publications from all countries, written in all languages, he is in a position to realise the very great advantage (referred to in an earlier page, p. 31) that results from the use of the learned tongues, in the terminology of zoological science. For the educated classes in all countries are equally acquainted with these; and when half of a sentence consists of words of Greek or Latin derivation, the labour of translation from a foreign tongue is necessarily greatly lightened. To no writer is this advantage of so great importance as to the Englishman, who is usually less familiar with the tongues of other nations than his colleagues abroad. It will easily be understood that in the world of zoology, there is no "predominance of the English-speaking races." Far from it. German is the language which supplies the fullest literature of every scientific subject; and in England even our text-books are, for the most part, translated from the German. German, in short, is to the seeker after Knowledge, what English is to the seeker after Money.

Let us now pause a moment to consider how large a number of different industries profit by the labour of the zoologist. First there is the shipping trade; for, of course, all specimens from foreign lands are brought by sea. The chemist supplies preservative substances, and reagents used in the preparation of objects for the microscope. The construction of microscopes is a profession in itself, and one which employs many industries; for the making of a microscope includes not only the work of the optician, but also that of the artificer in brass, and of many other handicraftsmen. The glass-worker supplies "slides," that is to say, the thin pieces of glass upon which objects for the microscope are placed, and "cover-slips," the little sheets of thinner glass which are laid over them; and, besides these, the bottles in which specimens are placed. Then comes the microtome, already spoken of, by means of which sections for the microscope are cut; how many skilled workmen have been engaged in the construction of its parts! Sheffield, perhaps, has supplied the razor which it holds, as well as the instruments for the dissection of the larger zoological specimens. We have already spoken of the laboratory servants, and the bone-articulators and skin-stuffers, who are personally and directly employed by the zoologist; and of the artists and photographers who depict his specimens, or perhaps copy his drawings. We must add to the list of the zoologist's helpers, last, but not least, the printer who "sets" the learned treatise in which the final result of his work is usually embodied; and attendant on the work of the printer is that of the bookbinder. With the bookseller the zoologist has but little to do; the general public, even the reading public, has no knowledge whatever of the writings of the zoological specialist. They are addressed to his equals and co-workers, not to critics and reviewers. Their publication is provided for, not by the law of supply and demand, but by the funds of the learned societies and the universities. It is only occasionally that a writer arises who is able and willing, like Huxley or Darwin, to express himself in a book that the general public can read; and it is only after a lifetime of detailed work, such as is understood only by the specialist, that writers like these think it fitting to lay the results of their labour before outsiders.

The librarian, finally, must not be forgotten, in making up our list of the zoologist's helpers. The preservation and cataloguing of zoological literature is obviously a task all the more important, because, as we have already stated, zoological writings are not regulated by the law of supply and demand. A very little paper, read to a very small meeting of a learned society, and wholly ignored by the world at large, may contain facts priceless to the world of science. It is on the accurate and painstaking work of the librarian, who preserves and catalogues small things as conscientiously as large ones, that we rely for the completeness of our record of zoological knowledge. Such work has at all times been carried on in the libraries of our universities; but at the present time there are in existence libraries specially devoted to zoological literature alone.

The museum, again, must not be forgotten, in which our man of learning stores his specimens, duly labelled and arranged. Here, again, is a staff of curators and sub-curators; and, under their direction, work for various workmen, and for perhaps even a humble charwoman to dust the shelves.

Turn now to another aspect of the zoologist's work--that of teaching. We should think it very wrong to turn men loose on the world to practise in the professions of law or medicine without a long and careful training to fit them for their task. No less impossible is it for anyone to become a man of science without a similar training; for the profession of the man of science, whether zoologist, chemist, botanist, or expert in whatever branch, if defined in plain English, is the profession of seeking after knowledge of the order of things in which we live; and what profession can be more important to the world than this? To attain a scientific degree of any value, years of study are therefore required, and a series of examinations tests--or is supposed to test--the success of the student. Both the work of teaching and the work of examining must be the tasks of the scientist who has attained a position of eminence in the world of learning. The preparation of lectures, with their accompanying illustrations of diagrams and lantern slides: the guiding of classes engaged in the actual work of making acquaintance with animal specimens--these are the labours of the great man who is at the head of things. His task is carried out with the aid of junior helpers of his own profession--the demonstrators, who "point out" detail after detail of the work described in the lectures. Another helper, more esteemed by the students than by the professor who teaches them, is the "coach" who prepares them directly for their examinations. His aid, in the shape of extra teaching, given at the last moment, will often secure for the careless and inattentive pupil, better success than is the lot of the painstaking and industrious one, who cannot afford to pay extra fees.

Few, however, of all the many pupils who crowd the lecture room of the zoologist, will ever become zoologists themselves. A vast proportion of them are students of medicine, of whom some knowledge of the subject is required. Others are preparing to be schoolmasters or schoolmistresses, and seek just such an amount of knowledge as they expect to find useful in teaching pupils of their own. To the students who are preparing to be doctors or teachers, circumstances often assign a limit--"thus far and no farther"--when they would fain bring their knowledge to a higher standard. But the time they have spent already has not been wasted. How keen an observer of animal life is the country doctor! How often, isolated from the world of learning, and ill-provided with books, he finds in this his chief recreation! As for the schoolmaster, how is the routine of school-work relaxed, and labour changed into pleasure, when he lets his boys exchange grammar and Euclid for zoology, and the lessons of the schoolroom for lessons in the fields!

The most important part, however, of a zoologist's work is not the giving of instruction, but the labour of original research, to which we have already alluded; not the mere communication of information, but the task of adding to the general store of knowledge; not teaching, but discovery. The work of the man of science is, in fact, within the limits of his own department, the work of seeking after truth.

INDEX

Acoelomata, 37. Adaptation, 13. Alternation of Generations, 57, 137. Amoeba, 35, 45. Amphibia, 152-154. Ancestors, 40, 42. Animalcule (minute animal), 49. Anisopleura, 29. Annelids, 72. Annulosa, 69. Ants, 92. Appendages, 77. Arachnida (spiders), 84. Arthropoda, 33, 76. Ascidians, 33, 44, 135. Asexual reproduction, 55. Atavistic variation, 27. Azygo-branchiata, 29.

Balanoglossus, 133, 143. Barnacles, 79, 80. Bees, 91. Beetles, 95. Bell Animalcule, 49. Birds, 156. Bivalve shell-fish, 23, 27, 107. Body-cavity, 34, 37, 38. Body-cavity (diagrams), 38, 139. Body-rings, or "segments," 69. Brachiopoda, 33, 43, 44, 117. Bryozoa, 33, 44, 119. Buds, 55. Butterflies, 89, 93.

Cat, fur of black, 160. Cell, 11. Cell-types, 49. Cephalodiscus, 145. Cephalopoda, 113. Centipedes, 77. Chætopoda, 71. Chalk, 46. Chordata, 33, 44, 135, 143-146. Cilia, 42, 43, 48, 65. Classes, 33. Classification, 30. Classification, tables of, 30, 44, 52, 62, 67, 75, 116, 118, 121, 134, 146, 164, 179. Coelenterata, 33, 44, 53. Coelomata, 37, 44. Cockle, 111. Colony, 57. Corals, 59. Corallines, 56, 58. Corticata (or Infusoria), 47. Crabs, 81. Crocodile, 11. Crustacea, 78-83. Ctenophora, 60, 62.

Degeneracy, 28, 172-180. Development by metamorphosis (change of form), 41, 89. Development, direct, 45. Dicyemidæ, 34. Diploblastic (two-layered), 34, 36. Diploblastic larva, 41. Duck-mole, 160.

Earthworm, 74. Earthworm, diagrammatic section of, to show position of body-cavity, 38. Echinodermata, 33, 43, 44, 122. Ectoderm, outer or skin-layer of adult animals and larvæ (corresponding with the epiblast of embryos in the egg), 34, 37, 41, 139. Eleutheroblasteæ (hydroid animals which throw off "free buds"), 56. Embryology, 45. Encrinites, 131. Endoderm, inner or digestive layer of adult animals and larvæ (corresponding with the hypoblast of embryos in the egg), 37, 41, 139. Enteron, 36. Environment, 26. Errantia, or Wandering Annelids, 72. Euthyneura, 100.

Families, 33. Fertility, 32. Feathers, 157. Feather-stars, 132. Fishes, 150-152. Flagella, 65. Flat-fish, 23. Foraminifera, 46. Frogs, 38, 152.

Galeodes, a spider-like animal, 85, 86. Gasteropoda, 29, 98-107. Gasteropoda, classification of, 29. Gastræa, 40. Gastrula, larva, 41, 150. Genus, 32. Gills, 45, 141, 149. Grades, 34, 35-38. Gregarina, 49.

Heliozoa, 48. Hemichordata (or Adelochorda), 33, 43, 145. Hermit Crabs, 80. Holostomata, 105. Hybrid, 32. Hydra, 36, 41, 54, 59.

Infusoria 10, 47. "Infusorial earth," 47. Insects, true, 88-97.

Jelly-fish, 57, 58.

Kangaroo, 163.

Lamellibranchiata, 107. Lamp-shells, 119. Land Animals, 166. Larvæ, larval forms, 40, 41. Larvæ of Brachiopods, 119. Larvæ of Insects, 90. Larvæ of Molluscs, 115. Lancelet (Amphioxus), 41, 140, 149. Leeches, 71. Limpet, Common, 17, 19, 20, 29, 30. Limpet, Semi-transparent, 15-20. Liver-fluke, 71. Lobsters, 80. Lophophore, 117, 122. Lustre, metallic, of feathers, 157.

Mammalia, 160. Man, 13, 26, 167-180. Mantle (of bivalve molluscs), 108. Marsupialia (or Metatheria), 161. Marsupium or nursery-pocket, 161. Mesoblast, 38. Mesoderm or middle body-layer, 37, 61. Metameric symmetry, 70. Mesozoa, 35. Metazoa, 35. Microscope, 9, 10, 182. Microscope, Sections for the, 182. Microtome, 185. Mites, 87. Mollusca, 29. Mollusca (classification of Gasteropod), 29. Moths, 93. Monoblastic, 34. Moss-Corals, 33, 39, 119. Mule, 32. Mussel, Common, 103.

Nematodes, 71. Notochord, 135, 139, 145, 149, 151. Nucleus, 35. Nummulite, 46.

Odontophore, 100. Operculum (of univalve molluscs), 105. Opossum, 161. Orders, 33. Orthonectidae, 34.

Pelecypoda, 107. Perforating gills (of vertebrates and other chordata), 142, 144. Peripatus, 88. Periwinkle, Common or Edible, 19, 26, 105. Periwinkle, High-tide-mark (_L. rudis_) 19, 105, 114. Periwinkle, Yellow, 19, 21, 23, 25, 30, 105. "Persons" of a colony, 58. Phoronis, 122. Phylum, pl. phyla, 33. Placophora, 113. Planarian Worms, 37, 70. Planula Larva, 41. Platyhelminthes, 44, 71. Polycystina, 47. Polyzoa, 119. Porifera, 33, 63, 68. Protective Coloration, 15, 25. Protophyta, 50. Protoplasm, 35. Prototheria, 161. Protozoa, 33, 44, 45. Pseudopodia, 36.

Radial Symmetry, 53. Radiata, 53. Radiolarians, 47. Rainbow Worm, 72, 159. Reptiles, 154-156. Rhabdopleura, 145. Rhizopoda, 36, 46, 48. Rodent, Teeth of, 163. Rotifers, 76.

Sand-hoppers, 83. Sauropsida, 154. Scales of fish, 142, 143. Scallop, 107-112. Scorpion, 87, 88. Sex, 10. Sea-Anemone, 54, 59. Sea-Cucumbers, 129, 130. Sea-Fan, 59. Sea-Mats, 119. Sea-Mouse, 72, 159. Sea-Urchins, 23, 33, 122. Shell-fish, 33. Siphonostomata, 102, 106. Skin of Vertebrates, 142. Snail, 98, 114. Snake-Stars, or Brittle-Stars, 128. Species, 30. Spiders, 84. Spiny Ant-eater, 160. Sponges, 33, 44, 63, 68. Sponges, Parasitic, 68. Starfishes, 127. Streptoneura, 29, 100. Symbiosis, 48.

Teeth, 147, 163. Tentacles (arms or feelers), 54. Ticks, 87. Trichina, 71. Triploblastic (three-layered), 37. Trochophora, 43. Trochosphere larva, 42, 43, 72. Tubicolous (tube-dwelling) Annelids, 72, 74. Tunicata, 33, 44, 135. Turbellaria, 70. Two-layered animals, 34, 36.

Unicellular animals, 11, 34, 35, 39, 44. Univalve shell-fish, 98. Urochordata, 145.

Vacuole, contractile, 35. Variation, 24, 26, 28, 32. Varieties, 29. Vermes, 33, 44, 68. Vertebrae (joints of the backbone), 138, 139. Vertebrata, 33, 44, 138.

Water Animals, 166. Wheel-ball larva, 42, 43. White ants, 93. Wood-lice, 83. Worms, 33, 44, 68.

Zooids, 58. Zoologists (_see below_). Zoophyte, 53. Zygobranchiata, 30. Zoologists, names of-- Buffon, 11. Caldwell, 160. Chamisso, 137. Cuvier, 54. Darwin, 24, 76. Dubois, Eugène, 168. Forbes, 17. Gadow, 157. Gosse, P., 54. Grant, Robert, 65. Hæckel, 40, 168. Hertwig, O., 50. Huxley, 37, 78, 136, 154. Kowalevsky, 136. Landsborough, W., 109. Lang, A., 39. Linnaeus, 32, 68. Leuckart, 71. Morgan, Lloyd, 20. Parker, T. J., 32. Roberts, G., 21. Romanes, G. J., 11. Sharp, D., 92. Sollas, 65. Woodward, 109.

Transcriber's Note:

Obvious typographical errors have been corrected. Original published spelling and hyphenation have been retained as they appear in the original publication, including "debateable" and "cellless". A possible missing "wall" has not been added to the caption for Fig. 5 ("--muscular of intestine"; and reference to "the Italian poet" on Page 138 of the original publication has been preserved. Where figures or tables cut paragraphs, they were moved above or below the paragraph.

End of Project Gutenberg's Stories of the Universe: Animal Life, by B. Lindsay