may be stowed away and investigated at any leisure moment. For example, during a few weeks at the seaside, material for a winter's occupation may be very easily procured. Neither is there so much hurry in drawing, as when an animal is living we are afraid it may die. For the sake of controlling the observations made on the sections, sketches of the general structure may be made, thus enabling the student to remember where each particular section must have come from.

There, is however, one other consideration to be noted, namely, that every cut destroys a certain amount of tissue. Thus suppose that a worm, as in Figure 27, be cut transversely, a good deal will be destroyed; but if longitudinal sections be made of another specimen, then one will see parts that the cut destroyed before, and only those spots where the two sets of cuts would have crossed had they been on the same animal will be wanting in both series. But even if you merely make a second series of cuts they will not destroy transverse sections, exactly the same place as in the first series.

(FIG. 27.) Longitudinal and

the lines showing the cuts.

When only a few preparations of some tissue are wanted, this instrument permits a rapidity of work combined with a degree of nicety unattainable by any other means, and I do not hesitate to recommend it most highly both to those who are carrying on microscopical investigations and those who are forming amateur collections, for only a little care is requisite to enable even persons with unskillful or unpracticed hands to make preparations equal to the very best that have ever been produced.

To succeed in doing this, however, very great care must be paid to the way of preparing the object. The following method is applicable in a great many cases, in all, in fact, except where there is any fat to be preserved, or where, as is not unfrequently the case in histology, a special method of hardening or staining has to be employed: If the object is some small animal it may be killed by putting it in an 0.1% osmic-acid solution or in picric acid, and then in alcohol for twenty-four hours or less, according to the size of the object, and finally in absolute alcohol in sufficient quantity to entirely remove all the water from the object. For this purpose thirty or forty times the volume of the object is necessary. If the object is a bit of tissue or some organ it may be hardened in alcohol without any preliminary treatment. When the object is composed of loose tissue, and is not more than 3 m.m. in diameter, it may be colored in toto, thereby sav

ing a great deal of labor. This is done by putting it after it has been in absolute alcohol in a very weak carmine or hæmatoxyline solution. Either of these may be prepared by diluting the ordinary tinctures (Beale's carmine or Boehmer's hæmatoxyline) with about six times their volume of distilled water. Carmine usually gives the best results. The object must be left from twelve to twenty-four hours in the coloring solution, according to its size and nature, and then replaced in absolute alcohol for twenty-four hours.

It is sometimes convenient to use chromic acid for hardening tissues a little before putting them in the alcohol. In this case they cannot be easily colored in toto unless every trace of the chromic acid has been removed by frequently renewing the absolute alcohol, a troublesome process requiring a long time and large quantities of spirit.

The object once hardened, or colored and hardened, as the case may be, can be imbedded in paraffine by the following method: Place it in pure turpentine for half an hour, then five or ten minutes in a mixture of equal parts of paraffine and turpentine by weight, warmed so as to be liquid, and afterwards in pure, melted paraffine for five minutes. Great care must be taken not to have the paraffine warmer than is necessary to keep it liquid, otherwise the tissues will be ruined. The object should be moved about gently in the paraffine to free it from the turpentine adherent to its surface. By these processes the paraffine penetrates the whole object, giving it the best consistency possible for cutting.

The next step is to pour some paraffine into a little paper tray, then lay the object in it, and pour in enough paraffine to cover it over entirely, and leave it for half an hour or more to cool. The mass of paraffine, when solid, may be taken out, and trimmed down with a penknife to such a size and shape as will let it fit into the clamp of the object holder of the microtome; the part containing the object must project enough above the clamp to be struck by the knife as it is drawn along, in the way above described.

When the object contains fatty tissue which it is wished to examine more closely, it may be imbedded in the so-called transparent glycerine soap in the way that has already been in use for several years.

The sections when made are surrounded by paraffine, and usually curl up. They must be taken up with a fine-pointed brush,

barely moistened with spirits of turpentine, and then put on a slide and covered with a drop of turpentine, which dissolves in a few seconds all the paraffine. The sections can then be unrolled with the brush. If the object is colored in toto, the sections are all ready for mounting, which may be done by wiping off the superfluous turpentine with a bit of cambric. The addition of a drop of balsam (or better still of a mixture of one part Canada balsam and two parts white Dammar varnish) and putting on a cover slip complete the preparation.

If, however, the object has not been colored beforehand, the sections must be stained singly; to do this, when they have been imbedded in paraffine they must be left half an hour in a few cubic centimeters of spirits of turpentine, then one fourth of an hour in absolute alcohol, after which the alcohol should be renewed and the sections left for another quarter of an hour, whereupon they can be at once stained and mounted either in balsam or glycerine in the usual manner described in all hand-books of microscopy or histology.

This method of imbedding in paraffine has the great advantage that objects once prepared in this way may be kept indefinitely and be cut at any time, or even be partially cut, and then be stowed away to be cut again by and by, it being only necessary to cover up the exposed surface of the object by dropping a little melted paraffine upon it. I have a small collection of such objects, each one bearing a number referring to a catalogue, so that there are several things of which I can make a first-rate preparation in ten minutes at any time.

I have found it convenient in making long series of sections to designate each series by a letter of the alphabet, and after having been once through to begin anew AA, AB, AC, and then again BA, BB, BC, and so on, I am accustomed to put several sections on each slide, which are numbered. My catalogue shows what each series is, and also anything about any section I choose to note, thus: "W. Planaria tora, transverse sections, 2 (slide number) through the brain, III. (number of section) through the eyes. In this way any particular section out of many thousands can be quickly found.

The sledge microtome can be obtained of Thomas A. Upham, mechanician, 17 Harvard Place, Boston, Mass., for $25. The knives have, at present, to be imported from Windler, Dorotheenstrasse 3, Berlin C, where they cost 6 marks (2 thalers) apiece. But Mr. Upham hopes soon to be able to supply knives himself.

ON THE STUDY OF BIOLOGY.1

BY PROF. T. H. HUXLEY.

THE HE sense in which "natural history" was used at the time I am now speaking of has, to a certain extent, endured to the present day. There are now in existence, in some of our northern universities, chairs of civil and natural history, in which the term natural history is used to indicate exactly what Hobbes and Bacon meant by that term. There are others in which the unhappy incumbent of the chair of natural history is, or was, still supposed to cover the whole ground of geology and mineralogy, zoology, perhaps even botany, in his lectures. But

as science made the marvelous progress which it did make at the end of the last and the beginning of the present century, thinking men began to discern that under this title of natural history there were included very heterogeneous constituents, that, for example, geology and mineralogy were, in many respects, very different from botany and zoölogy; that a man might obtain an extensive knowledge of the structure and functions of plants and animals without having need to enter upon the study of geology and mineralogy, and vice versa; and further, as knowledge advanced, it became clear that there was a great analogy, a very close alliance, between those two sciences of botany and zoology which deal with living beings, while they are much more widely separated from all other studies. It is due to Buffon to remark that he clearly recognized this great fact. He says: "Ces deux genres d'êtres organisés (les animaux et les végétaux) ont beaucoup plus de propriétés communes que de différences réelles." Therefore it is not wonderful that at the beginning of the present century, and oddly enough in two different countries, and, so far as I know, without any intercommunication between the respective writers, two famous men clearly conceived the notion of uniting the whole of the sciences which deal with living matter into one whole, and of dealing with them as one discipline. In fact, I may say there were three men to whom this idea occurred contemporaneously, although there were but two who carried it into effect, and only one who worked it out completely. The persons to whom I refer were the eminent physiologist Bichat,2 the great naturalist Lamarck, in France, and a distinguished 1 Extracts from a lecture by Professor Huxley, delivered at the South Kensington Museum, on Saturday, December 16, 1876.

* See the distinction between the " sciences physiques" and the "sciences physiologiques" in the Anatomie Générale, 1801.

German, Treviranus. Bichat assumed the existence of a special group of "physiological" sciences. Lamarck, in a work published in 1801,1 for the first time made use of the name "biologie," from the two Greek words which signify a discourse upon life and living things. About the same time it occurred to Treviranus that all those sciences which deal with living matter are essentially and fundamentally one, and ought to be treated as a whole, and in the year 1802 he published the first volume of what he also called Biologie. Treviranus's great merit consists in this, that he worked out his idea, and that he published the very remarkable book to which I refer, which consists of six volumes, and which occupied him for twenty years, from 1802 to 1822.

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That is the origin of the term "biology," and that is how it has come about that all clear thinkers and lovers of consistent nomenclature have substituted for the old confusing name of natural history, which has conveyed so many meanings, the term biology, to denote the whole of the sciences which deal with living things, whether they be animals or whether they be plants.

Having now defined the meaning of the word biology, and having indicated the general scope of biological science, I turn to my second question, which is, Why should we study biology? Possibly the time may come when that will seem a very odd question. That we, living creatures, should not feel a certain amount of interest in what it is that constitutes our life will eventually, under altered ideas of the fittest objects of human inquiry, seem to be a singular phenomenon; but at present, judging by the practice of teachers and educators, this would seem to be a matter that does not concern us at all. I propose to put before you a few considerations which I dare say many of you will be familiar with already, but which will suffice to show — not fully, because to demonstrate this point fully would take a great many lectures that there are some very good and substantial reasons why it may be advisable that we should know something about this branch of human learning. I myself entirely agree with another sentiment of the philosopher of Malmesbury, that "the scope of all speculation is the performance of some action or thing to be done," and I have not any very great respect for or interest in mere knowing as such. I judge of the value of human pursuits by their bearing upon human interests, — in other

1 Hydrogéologie, an. x., 1801.