the student works his way from the known to the unknown; candidly ignorant; frankly teachable; critically exact; the attitude of mind that led Kepler to outline seventeen different hypotheses and seventeen different sets of laboratory observations and computations before he was ready to announce to the world that he had discovered the “shape of the path of the planet."

II. THE PURPOSE OF THE MICROSCOPE

J. B. LILLARD, TEACHER OF BIOLOGY, WILLIAM MCKINLEY HIGH SCHOOL,
ST. LOUIS, MO.

One who has taught nature-study in the grades, biology in the high school and the university, and has worked with candidates for advanced degrees in the subject, sees the value of the microscope varying from zero to one hundred. In the grades, where the work is mainly extensive, its use is hardly to be thought of. Possibly in the last two years of the high school and surely in the university, its use is all-important. In the last instance biology would be a farce without it. But in most of the high schools of this country zoology, botany, and human physiology are presented in the first two years of the course.

The purpose of the microscope whenever used is obvious. Our high schools are not for the purpose of training pupils to become experts in the use of microscopes. I say this fully realizing that it has revealed a great body of biological facts, and that even those facts and principles which are not the direct result of microscopic study are nevertheless intimately linked and fused with the revelations of the lenses. I realize, too, that microscopic study is distinctly a biological method. In any scientific study the methods of the science are of great value. In some cases they surpass in value even the facts and principles of the subject itself. The omission of microscopic observation, when the child is mentally ready for it, would find a parallel in the study of chemistry by totally disregarding qualitative tests or by completely eliminating the use of balances.

In the first two years of the high-school course we are dealing with children. We must employ many means of approaching the subject. We must take into account the child's experiences and previous preparation. Dissections, models of whatever kind, physiological demonstration, experiment, and observation, fieldwork, textbooks, illustrations, figures, lantern slides, lectures, recitations, question boxes, microscopes-simple, dissective, and compound-and what not, may all be used to advantage. But in every case it must be remembered that each of these and perhaps many other devices are simply means to an end in the study of life. Not one of them should be used for its own sake, but only as a tool absolutely subservient to the needs of the course.

I have seen the energy, time, and enthusiasm of a class dissipated in the search for something that could not be found. On the other hand, I have seen the indifference of the same class suddenly transformed into intense eagerness as soon as a little obstruction had been removed by a single glance thru the eyepiece of a microscope.

The purpose of the microscope is to reveal what is essential to a clearer understanding of the subject. Whenever it becomes necessary to complete a chain in the development of a subject by supplying the microscopic link, then use it. This link will be pluralized (if I may coin the expression) as we go from the first to the fourth years in the course because the character of the work will necessarily change as the pupil develops. But the "big eye" as it is termed in college slang, must lead us out of chaos not into it; it must be a helper, not a burden; it must be looked thru and not at. In a word it must be a means

and not an end.

THE USE OF THE MICROSCOPE

Assuming that biology is given in the first two years of the course (and my high-school experience in the subject has been limited to this), I am compelled to discourage a wholesale use of the instrument.

Pupils entering from the grammar schools find difficulty in orienting themselves for reasons obvious enough to one who has had any practical experience in secondary-school work. Taking it for granted that the pupil has learned how to manipulate the instrument and that there is plenty of time for the purpose, he may grope about for hours, yes even days, in the vain endeavor to find anything. I have spent a great deal of time showing the pupil what I wanted him to observe only to discover later that he had wasted much valuable time on a bubble. It is a pedagogical crime to presume that the Agassiz method can ever be used on a child at work over the microscope. It is my honest opinion that it would be disastrous even in the senior year of the high school. However, this has not been verified by experience. Very few first- or second-year pupils have the power of sorting out the essential details. If the teacher finds it is possible he can always handle the exceptional case. If the teacher is alive to the situation and employs the individual method as we do in the McKinley High School, this exceptional case will in no way disconcert him.

Referring again to the inability of the average, yes, even the vast majority, of our firstand second-year pupils to sort out essential details, I would say that even as grown-ups we form a mental picture and draw an interpretation rather than an accurate representation of the things we are studying.

I have found that manual-training pupils have some advantages over their fellows in seeing fractional values. But this advantage is after all only slight. And, as yet, how many actually get it? Nothing short of abnormal precocity can put a grown-up's head on a child's body.

Whenever the microscope is used the objects to be observed should be such as can be seen clearly. Much care must be used in selecting material that is not confusing. The idea that the real thing must be seen to be fully understood is good both in theory and in practice but to see the real thing, to see it as it is, and to see it in its proper relations is no easy task. When the boy or girl looks thru the eyepiece of a compound microscope he is looking into a new world. It is much more difficult than looking thru a telescope at the moon. It is much farther removed from his experience; and readjustment and reconstruction are much more difficult.

The projection microscope may be used to some advantage. Yet here again we are confronted with two handicaps: first, detail is generally eliminated; second, demonstration of minute structures is quite out of the question.

I have found the lantern to be one of the most important aids in presenting biological work to high-school pupils. The pictures are generally diagrammatic and interpretive; all unnecessary and confusing material is eliminated, and the pupil sees what is

essential.

Now, all that I have said refers mainly to the anatomical side of biology, for reasons obvious enough. But I want to emphasize my belief that the physiological side has been shamefully neglected both in zoölogy and botany; yes, and strange as it may appear, even in human physiology.

To recapitulate: The importance of the microscope will depend very largely on the position of biology in the high-school curriculum, that is, whether it is offered in the first, second, third, or fourth year of the course; that whenever employed, whether in zoölogy, botany, human physiology, or whether in that phase of both the last two, known as bacteriology, it is to be used only when necessary to supply an absolutely essential link in the chain of development. I believe it is indispensable for the most effective teaching, but that the extent to which it may be used must depend on the mental development of the pupil; that it is, after all, only one of the many ways we have of giving the student a glimpse at the most wonderful thing in the world-life and of acquainting him with the most important contribution of modern biology to the philosophy of life-organic evolution.

III. THE KINDS OF MICROSCOPE WORK VALUABLE FOR HIGHSCHOOL STUDENTS

H. F. WEGENER, PRINCIPAL HIGH SCHOOL, TACOMA, WASH.

The history of the development of the microscope as an instrument of investigation is so closely related to the history of the growth of the biological sciences that, in order to understand the latter, we are obliged to make ourselves familiar with the former. The improvements in the one made possible the discoveries in the other.

Of all instruments for scientific research none has such an interesting history as that of the microscope. If we compare the simple magnifiers used in the sixteenth century with the complex instruments of today, what a wonderful change has it undergone.

With its gradual approach to perfection there was a corresponding expansion of its field of application, until today there is no other instrument of investigation that can approach it in the variety and extent of its uses.

So greatly have these been multiplied that it is difficult to name an industry or field of research in which some form of the microscope is not used.

A period of nearly 150 years intervened between the beginning of the use of the simple convex lens and the evolution of the achromatic objective. It was not until 1830 that the modern objective, in its cruder form, first began to be used. All we know about the minute structure of living organisms has been learned since that time.

It is true Lieuwenhoeck made some remarkable observations with his little globules of glass a hundred years ago and thereby drew the attention of the curious to the study of minute objects. His discoveries gave the stimulus and incentive to others and indirectly to efforts to make improvements in the instrument itself.

In this way many isolated facts were collected but no attempt to correlate this knowledge and make it a basis for scientific investigation was made until twenty years after the achromatic objective had been invented.

There was a time, in the memory of many of us, when the microscope was looked upon as merely a kind of scientific toy. Many persons interested in objects of nature and of an inquisitive turn of mind bought microscopes. For their benefit books were published bearing such titles as the following: Evenings with the Microscope, The Wonders of the Microscope, The Microscope and Its Revelation, etc.

Societies were organized in which eligibility to membership consisted in the ownership of a microscope. A national organization, called the American Society of Microscopists, was formed. This society existed for a number of years and was finally merged as a section with the American Association for the Advance of Science. A similar society, but of much earlier organization and counting among its members many men of great scientific attainments, was formed in England and called the Royal Microscopical Society. A great deal of the knowledge thus obtained was not of a scientific character. It was merely a collection of facts about objects which could not be seen by the unaided eye. They were interesting, because they were new and because they appealed to the curiosity of the observer. This sort of study had its value, however, for subsequent scientific purposes, for the students learned and discovered many facts concerning the technic of preparation of objects for microscopic study. Many of these men became experts in the manipulation of the instrument and what they thus learned later on greatly aided the scientists in their work of investigation.

A large body of facts drawn from the realm of nature had thus been accumulated before any serious attempt was made to organize this knowledge and make use of it in the pursuit of further scientific investigations directed in particular lines of research.

The introduction of the microscope as an instrument of research in high-school science in this country had its beginning with the appearance of the American edition of Huxley's Elements of Biology in 1877.

Previous to this time the use of the compound microscope was deemed impracticable

for the reason that high-school students were too young to learn to manipulate the instrument. As evidence of the feeling, I need but refer to the preface in Gray's Textbook of Botany, in which this is given as a reason why the study of the Cryptogams is omitted from this book. On account of Professor Gray's position as a botanist in this country, his dictum was received without question, and for ten years longer few attempts were made to extend the study of botany in high schools to the lower forms of plant life.

The appearance of Sach's Textbook of Botany in 1884 with its new classifications of plant forms and the broader view it gave by including structure and function as essential to a correct understanding of plant life, made the use of the microscope necessary.

Teachers began to learn that the difficulties in the manipulation of the instrument were not so great but that students of high-school age, with a little instruction and practice, could do profitable work. A similar change took place in our method of teaching zoölogy. The new science, introduced by Huxley under the name of biology covering both fields, was now given a place in the high-school curriculum.

With this brief historical sketch of the evolution of the microscope and its gradual application in scientific investigation, we are brought to the time when the modern laboratory methods of teaching the biological sciences in our high schools had their beginning.

In describing the kinds and amounts of microscopic work valuable for high-school students, I shall confine myself largely to my own experience in teaching. I do not pretend to say that these are all the applications of the microscope that can be made in teaching the subjects that I shall mention, but that they are such as I have found by experience to be possible and valuable.

The fundamental fact that, in all our studies of living organisms, should constantly be born in mind is this, that no matter how great the variety of form and structure of the organs which make up the individual as a whole, the life of the individual is the sum of the life activities of all the cells. The more we know of an organism the better we are able to understand its various activities and the conditions under which it can live and grow and multiply.

Since it is impossible, on account of the time limit that is set to the various subjects that are presented for study in a high-school course, to study many forms of plant and animal life, it becomes necessary to choose for our study such forms as best represent the typical structures of the different classes. There may be some difference of opinion among teachers as to what are the best types. Then, again, there is also the matter of availability of material. It is not always easy to find the best types in the vicinity in which you happen to live and you are therefore compelled to choose some related type as the material for study.

The examples which I shall give, which require the use of the microscope, lay no claim to logical order of study but are merely given as illustrations of what may be done profitably by high-school students.

Beginning with the plant world, I would choose, on account of its simple structure, its large transparent cells, and its abundance in all ponds and slow flowing streams, the alga spirogyra. It lends itself as an interesting study of the phenomenon of cell growth and cell division, of the properties of chlorophyll, of starch production, of conjugation, and spore formation.

In Vaucheria, another one of the algae, we see a different but simpler structure with a form or reproduction resembling that of higher plants. As an example of a unicellular plant, the protococcus gives us a view of multiplication by simple cell division with a motile stage.

A study of the fungi is valuable on account of their practical relation to household economy. A knowledge of their growth and reproduction gives the housewife an intelligent insight and reason for the various means she uses for preserving fruit. The common green mold, penicillium glaucum, and the white mold, mucor mucedo, are the best subjects for this study.

Another plant whose product profoundly affects the welfare of man, is yeast. From its study we learn that it is a plant because it has the power of constructing protein from inorganic substances, that it multiplies by budding or gemmation, that it is killed by heat, that it is the cause of fermentation in all liquids containing sugar, by decomposing the latter and that the product of this decomposition is alcohol. It has a practical value for the housewife in that it teaches her the secret of bread-making.

The liverworts, mosses, and ferns should receive attention because in these three classes of plants we are introduced, besides difference in structure, to a feature in plant reproduction known as alternation of generation. Its two distinct sexual organs, the archegonia and antheridia, differing in form and very unlike the same organs in flowering plants. The lichens, so frequently called mosses, deserve notice not only on account of their wide distribution in nature but as an illustration of that singular phenomenon called symbiosis in which an alga and a fungus keep house together and form a single organism.

In this connection, the historical fact may be mentioned that for 300 years the true character of a lichen remained a puzzle to botanists until the riddle was solved by the studies of Bornet in 1860.

The use of the microscope is essential in the study of the histology of the spermatophytes and the organs of reproduction, such as the stamens and the formation of the pollen, the stigma, style, and ovary with its contents. The function of the leaf as determined by its structure, its epidermal cells, its stomata with their guard cells and their relation to the respiration of the plant; the intercellular spaces, the mesophyll with its chloroplasts and other products.

The structure of the stem with its fibro-vascular bundles, its bast fibers, and sieve tubes. The difference in structure of the Monocotyledonous and Dicotyledonous stem. The structure of the root, with its rhizoids and their cells and the osmotic action of the inclosed protoplasm.

In zoology, we need the use of the microscope in the study of all the unicellular organisms and in the histology and minute structure of the organs of the more highly organized animals.

I know of no better organism with which to begin this subject than the amoeba. We have here a bit of protoplasm exhibiting all the manifestations of a living being in its simplest form, contractility, irritability, and the whole series of processes included under the term of metabolism.

This study has another value for those who subsequently take a course in human physiology for it makes clear to them the peculiar function of the leucocytes of the blood acting as phagocytes.

Their amoebid character and their mode of injestion can only be understood by recalling to mind the study of the amoeba. Other unicellular organisms such as the vorticella and paramoecium, should follow to show differentiation of cell wall for special purposes.

The simple multicellular hydra, the fresh water sponge, the insect with its mouth parts, its nervous system, its spiracles and tracheae, the minute anatomy of the higher animals such as the clam, the earthworm and the crayfish, all require the aid of the microscope to understand their structure.

In the study of the human body the function of many of the organs can only be understood by careful study of their finer structure. For this purpose, carefully prepared sections of the human skin, to show sweat and sebaceous glands, and sections of the small intestines to show the villi, should be studied.

Ciliated cells of the air passage should be seen in order to show their relations to dust in breathing. The function of the kidneys is made clear by observing the structure of the glomeruli and Henle's loops. The double character of the muscle fibers of the heart, and the structure of voluntary and involuntary muscle fibers should receive attention.

The circulation of the blood through the capillaries cannot be understood until your pupils see it in the web of the frog's foot or the tail of a small fish.