THE RELATION OF A HIGH SCHOOL SCIENCE TEACHER TO INSTRUCTION IN AGRICULTURE.

PROFESSOR F. s. kĘDZIE, MICHIGAN AGRICULTURAL COLLEGE.

It has always been a matter of curiosity to me that the first substances studied by mankind in his efforts to solve the riddle of the universe were the farthest away from him. They were never the materials upon which he could place his hand or those with which he daily came in contact. You need but think of the early discoveries in astronomy and contrast those with the later discoveries in physics to be convinced of the truth of my statement. Little by little our schools begin to believe that what must be taught are those things which one needs to know in everyday life. Professors and school boards flatter themselves that they are the ones who determine what shall be placed in the curriculum of the school, but we now realize that the demands of the public for light to guide their feet is much more weighty than any decision of what shall be taught promulgated by the most learned pedagogue. Yielding as all our schools must to this outside pressure has come latterly the establishment of courses in agriculture in our high schools. These courses of necessity must be elementary, yet in order to be of any worth, viewed from either a practical or pedagogical standpoint, they must be founded on the facts of elementary science which should, so far as possible, be taught in connection with the teaching of agriculture. Knowing this, is the reason that I have selected this topic for review. The science teacher in the high school must put forth decided effort to correlate his subject with the agriculture taught in his school.

At the outset we must recognize that every book on elementary chemistry has so far devoted its attention away from everything looking toward the chemistry of plant and animal life. The reason for this condition of affairs is very obvious to me. It was easier to illustrate the elementary chemical principles by referring to the manufacture of acids, alkalies and metallurgy than to go into the mysteries of the transformations brought about in the surrounding matter by plants and animals and I do not believe now that it will be possible nor advisable in a high school course in chemistry to eliminate much that is now taught in our high school courses, but I do believe that in addition to what is now given, the pupil should work a certain amount of time with material which will bring him into direct contact with the processes of both growth and development of plants and animals. The easiest way perhaps to make clear my idea is to suggest certain experiments which have an important bearing: First with plants-By experiment prove that in the germination of seeds oxygen must be present. This is readily done by sealing up moistened seeds in glass containers containing various elementary gases such as (a) Hydrogen, (b) Nitrogen, (c)

CO, (d) Pure Oxygen, (e) Air. Prove that CO, is produced in germination by aspirating air through a bottle containing germinating seeds over into a second bottle containing Limewater or Barium Hydroxide. Prove that Oxygen is produced by leaves growing in sunlight by placing vigorous growing leaves in water charged with CO2 placed in a flask surrounding the leaves in sunlight. Other interesting experiments that may be tried showing conditions for plant growth are the germination of seeds on pure moistened cotton and after the germination is complete and the plant withers weighing the dried partially developed plant to prove to the student that the seed weighed more than the plant and that germination alone involves loss of weight. These are but mere suggestions illustrative of what may be brought to the attention of the pupil studying plant growth.

The National and State Laws have been educating the people regarding the matter of food but only in a narrow and technical way, however the enforcement of these laws has awakened a deep and widespread interest in the subject of foods in general. Many teachers have seized upon the public interest thus awakened and have created a great deal of enthusiasm. among their pupils along the line of detection of food adulteration, the improper use of preservatives, etc. This kind of work does not appeal to me as being at all in the line with the influence which we desire to foster in the school room. It belongs more properly in the police and justice courts. Children are not benefited by having the dishonest methods of some business enterprise exploited. What the children should be given are some basic idea regarding food which belongs to their everyday life and the life of their surroundings.

The human body as well as the bodies of all our domestic animals may be roughly characterized as an internal combustion engine composed of protein which uses carbohydrates and fats as a fuel, and as with all machines there is a constant wearing away of the material of which the machine is made, viz., protein, there must be a steady and continuous supply of this material in addition to the proper amount of energy supplying food ingredients. While the study of protein substances brings us into direct contact with the most complex and as yet least well understood molecules, still on account of its unique relation to animal life and nutrition merits the consideration of every chemistry teacher who aims to give a course that will help his scholar to think whether he becomes a chemist or never again turns his attention in that direction. One of the most difficult subjects for the beginner to grasp is the relation which experience has shown must be maintained between the protein and carbohydrates of a ration, or in other words, the nutritive ratio. This ratio can only be made clear and the elementary beginning knowledge of nutrition be obtained by chemical methods. There must be less talk before our high school scholars and more work done with them of a laboratory character which will give them a definite idea of what protein is and how it is determined. In fact, I believe

that the estimation of the amount of protein material is not so difficult, involving as it does the determination of Nitrogen, but that any high school could undertake the work. The use of the Babcock test bottle has been a revelation to many high school students regarding the subject of what milk is, but if in addition to the work with the Babcock test bottle we took up the matter of the determination of protein in milk and other food substances we could place a great many facts before the student which he could use and would be benefited-when considering the ideas which lead from a protein determination. There is nothing about the Soda Lime method or the Moist Combustion method of Kjeldahl* which cannot be mastered by any high school student and by the use of either of these methods the key which unlocks the mysteries of food and balanced rations is in his hand. The chemistry teacher of the high school can if he will help the teacher of agriculture to the greatest extent if he trains his pupils so that they will

*Determination of Nitrogen by the Kjeldahl Method (modified).

The Digestion :

Two grams of the material are brushed into a Kjeldahl flask which must be clean and dry. Twenty c.c of C. P. H2SO, are introduced and lastly a piece of cryst. CuSO, weighing about 2 gms. The flask is then placed on a rack under the draft hood and heated,--no gauze or asbestos being used to support the flask. The heat is applied very gently at first and if the flask froths caution is used to obviate boiling over of the contents. The digestion is completed when the solution becomes clear and light colored. The flask is allowed to cool on the rack to room temperature.

The Distillation:

To receive the amonia gas evolved, 30 c.c of N/5 H2SO, are measured from the acid burrette into an erlenmeyer flask, a little cochineal indicator added and the flask placed beneath the condensing tube leading from the distillation flask.

200 c.c of the tap water is measured out and added to the cooled flask containing the result of your digestion. This solution is then ready to be made alkaline and the distillation started.

Light the lamp on the distillation bench belonging to your distillation flask. Then drop into the flask a piece of mossy zinc, and finally measure out and add 75 to 100 c.c conc. NaOH solution to the flask,-connect immediately to the condenser and shake the flask thoroughly until you are sure the acid and alkali are well mixed.

NOTE: (This "thorough mixing" of the acid liquid and the added strong NaOH solution must not be neglected).

Put the lamp under at once and distil until from 200-250 c.c of distillate has been obtained in your receiving flask.

Stopping the Distillation:

Before removing the lamp always disconnect the flask from the condenser by loosening the cork in the neck of the flask, then turn out the lamp. Next remove receiving flask and find by titration with N/5 alkali how much of the 30 c.c of N/5 H2SO was neutralized by the NH liberated in your experiment. From this calculate the weight and percent of Nitrogen in the substance. N. X 6.25 Protein.

NOTES.

=

(a) Copper Sulfate is used as a transfer agent to carry Oxygen from the H2SO to the material being digested. The digestion with conc. H2SO, is an oxidation process.

(b) This method for Nitrogen is applicable to all materials containing this element except Nitrates and Nitrites (i. e., oxidized Nitrogen). Bringing a Nitrate in contact with H2SO, would involve loss of Nitrogen on account of escape of HNO, vapor.

know by actual personal knowledge what is meant by the term "Protein of the Food."

The longer I teach the more I believe that our greatest mistakes are in attempting to teach too much and the wrong kind of material. Three times a day your scholar is trying the effect of a properly or improperly balanced ration on his body while nothing is offered to him in the laboratory course which gives him the least light regarding the matter. The farmer, when it comes to beef and milk production, says he must know how much protein he is feeding and the answer to his inquiry should be sought from the teacher of chemistry who should enlist the members of his class in attempting the work of testing the food fed by the farmer.

In conclusion therefore I recommend:

I. That the high school science teacher without neglecting the present method of teaching the general principles of chemistry should direct the attention of his pupils to the simplest facts involved in the nutrition of both plants and animals.

2. That the determination of protein quantitatively by the student in a variety of substances used as food for man and animals best opens the way for an understanding of the principles of nutrition.

MATHEMATICAL CONFERENCE

REVOLVING VECTORS

PROFESSOR GEORGE W. PATTERSON, UNIVERSITY OF MICHIGAN

A little more than a century ago a most valuable extension was made in the domain of algebra when Caspar Wessel discovered that direction as well as magnitude might be represented analytically. Text books of algebra have made little use of this discovery though it has been greatly developed in works on the theory of functions of a complex variable, vector analysis and quaternions, and has been extensively used by physicists and electrical engineers. The reason why so little use of this discovery has been made by text books on algebra is not hard to find. Conservatism and the desire to keep general works on algebra within reasonable limits would be a reasonable explanation. However, I venture to address you on the subject, as I believe that anything which makes negative and imaginary numbers more reasonable to high school pupils would be a great gain to the teacher of algebra.

The concept of a vector quantity is primarily geometric, for it requires for expression both magnitude and direction. Evidently a revolving vector has a continuously changing direction while the magnitude may be constant or variable.

Before taking up my main subject, let me turn your attention to negative and complex numbers.

Early in the study of algebra every boy and every girl has the difficult task of mastering the idea of negative numbers, and I fear in many cases the idea is made too difficult to be mastered. Common sense tells us that, in the nature of things, an amount less than nothing is an absurdity. I believe that we all do agree-and must agree-that in actual fact quantities less than nothing at all do not and cannot exist, and that negative numbers or quantities are a conventional way of expressing real and positive things. Let us therefore examine negative and imaginary numbers and quantities with a view to showing their meaning and the uses to which they may be put. Many quantities are found in pairs, such as debit and credit, up and down, east and west, north and south, along a line and back again, acceleration and retardation, right-handed and left-handed rotation, tension and compression, and others too numerous to mention. In problems involving any one of these quantities we understand a negative answer to indicate not that the answer is absurd, but that the other one of the pair is to be understood.

To illustrate this, let us have the following problem:-The point B is five miles east of A, the point C is ten miles east of A. How many miles is B east of C? We reach the answer that B is 5 miles east of C. The ancients who lived before the invention of negative numbers would probably have declared that the answer denoted the impossibility of the problem, for it is evident that B is not east of C at all. Many pupils beginning algebra would agree in this verdict. The modern explanation is that the negative sign is to be understood as an operator which converts an eastward into a westward sense of measuring distances, and that the point B is found to be five miles west of C. Thus we see that we are not required to contemplate a distance of five miles less than nothing, but merely to recognize that east and west are converted into one another by reversal. We thus find a use for negative numbers and thereby save them from relegation to the category of absurdities. It is to be observed that we have thus added a new meaning to the sign minus, previously used for subtraction alone, and also for the sign plus, previously used for addition only.

In the above discussion of negative quantities, it has been noted that the negative sign is an operator which performs the function of reversing the direction or sense in which we count, as from eastward to westward. The result would be meaningless if we were not dealing with one of a pair of oppositely directed quantities. It evidently would be absurd to require