with the given telephone exciter, or sound intensity; or over four times as much as a good plate pinhole (caet. par.). The glass probe is essentially a hollow truncated cone, so that the oscillating air current strikes a sharp circular edge. Pressure is observed in the interior of the cone, and dilation (relatively) on the outside. If we imagined an air current toward the inside were converted into pressure, whereas an outward jetlike current were not, at least in the same degree, we should simulate the action of the probe. Being an embouchure the need of an optimum diameter of pinhole is implied; but it will presently appear that the need of a sharp edge is even more imperative, and it seems natural that there should be more vorticity on one side of the pinhole than on the other.

In many respects, however, the plate embouchure is more interesting, for here one can easily modify the bore and edge character of the pinhole, which in case of the glass quill tube cone has to be ground sharp to size. I have, therefore, given further attention to the simple plate device and the more important results are recorded in Figs. 2, 3, 4, the abscissas merely indicating the consecutive experiments. It was further found that the direction of the initial current in the

telephone made considerable difference. latter is provided with a switch and its first position (I) is indicated by open circles, the opposite position (II) by black circles. It was thought that the difference was merely an expression of less efficiency of the telephone in the former case; but this is not true, as so many of the black circles are negative increments in s. In each case, the plate pinhole probe (plate on a quill tube 2 cm long, .35 cm in diameter) was tested both in the salient (s) and the reentrant (r) position in relation to the U-gauge (see Fig. 1). Diameters of the pinholes pricked by a fine cambric needle are also given. The very fine pinholes (diam. .02 cm) are singly too slow for convenient use. Finally the thickness, t, of the foil (plate) in which the pinhole is pricked from the outside of the tube is entered, making the record complete. Fig. 1 gives the adjustment of quill tube be with pinhole at g to the pipe p actuated by the telephone at T, and the interferometer U-gauge, U. Pipe, spring break of the circuit and electric oscillation are in tune with the relation of bg (6.5 cm) to gc (10 cm) corresponding to a maximum fringe displacement s.

Pinholes Nos. 2, 3, Fig. 2, are similar but of vary ing size. The diameter effect within its range is not

definite, showing that some other factor determines its behavior. The salient pinhole in position I is, as a rule, strongly positive; the reentrant behavior in position II more strongly negative, but there are many Exceptions.

Pinholes Nos. 1, 0, 4, 7, Fig. 3, were punctured in much thinner aluminum foil, and the favorable effect of this is at once apparent in the improved efficiency of the probes. In other respects the remarks already made apply. Nos. 4, 7 were constructed with greater skill.

These experiments at once indicate the nature of the missing factor; for heretofore the thickness of the foil has been ignored. It is clearly of greater importance han the diameter of pinhole.

Following this suggestion I next pricked pinholes in mica plate, split as thin as admissible and much below .01 mm. The results in Fig. 4 show the enorously increased efficiency obtained, ordinates being even five times as large as those in Fig. 2, referring to the original thick foil. No. 5 was only examined for diameter .02 cm. In No. 6 there is but little diference between the first two diameters. In puncturEng the third, the hole was accidentally frayed to about twice the area wanted and beyond the admissible range. Hence the low efficiency.

There is, however, always difficulty in successfully enlarging the pinhole. For instance, in No. 8 the riginal efficiency (diam. .02) is very large, particuarly in the negative. On enlarging the bore to .035 and .042 cm, its sensitivity is nearly lost. No. 9 is nother peculiar case, in which the fine pinhole is egative in the salient and positive in the reentrant osition, a rare inversion of the usual occurrence.

The final graph shows the corresponding behavior of an efficient glass pinhole, one of the best. The fine ole mica probe is thus of the same order of excel

ence.

If we take the highest of the s values corresponding ▷ any thickness of foil, and plot s against , we et a graph of hyperbolic contour, giving a mean estihate of sensitivity based on the results obtained. The mallest manageable thickness of plate is thus essenial; in other words, the pinhole should be a sharp ircle and anything of the nature of a capillary tube, owever short, is detrimental. The viscosity of air is ere liable to ruin the experiment.

And yet the two sides of the pinhole behave quite ifferently to the current of air propelled through it the alternating nodal pressure. Hence the producon of vortices at the pinhole by the acoustic pressures ems alone to account for the observed results. The cillating air columns in contact and in opposite hases at the pinhole are successively shooting vorees into each other and the pressure difference results

because, owing to the structure of the pinhole in question, one of the air columns does this more efficiently than the other. As the pinhole dominates, the hydrodynamic forces in pulsating media (Bjerknes) have no relevancy. CARL BARUS

BROWN UNIVERSITY

THE NUTRITION OF PLANARIAN WORMS

PLANARIAN Worms exhibit differences in growth capacity according to their diet. They eat animal tissues with great readiness and show resulting variations in growth, depending upon the variety of tissue used and upon its condition as well. The worms thrive upon raw liver and have been kept indefinitely in our laboratory upon this as an exclusive diet. It was found,' however, that the power of liver to promote growth was diminished by heat and that the diminution depended upon the temperature to which the liver was subjected and upon the time of the exposure. Brain cortex is also an excellent food for the worms, and its power to promote growth is likewise diminished by heat.

In an attempt to determine whether the principle so important for the well-being of planarian worms could be separated from the intact tissue, the following procedure was employed. Liver from freshly killed guinea pigs was ground with sand and an equal weight of ether. The resulting paste was spread in a thin layer upon large glass plates and dried by an electric fan at room temperature for several hours. At the end of the drying the liver, which was in a highly friable condition, was ground to a fine powder in a mortar. It was then extracted five times with amounts of ether equivalent to the original weight of the liver, and the ether extract was evaporated with the electric fan. The product was a vaseline-like, brownish paste.

In all our experiments Planaria maculata was used. Each experimental group was kept in a finger bowl and consisted at the beginning of thirty worms. Since planarian worms multiply by fission neither average lengths nor number of worms alone could express the total growth, and it was decided to use as an index the total length of all the worms in a group. The length of the worms was estimated by placing them in a Petri dish over a piece of polar coordinated paper covered with a glass plate. As the worm

glided along fully extended its anterior extremity was centered upon the center of the paper, and by following the movements of the worm with the Petri dish a really satisfactory estimate of the length of

1 Wulzen, R., Univ. of Calif. Pub. Physiology, 1926, VII, 1.

the worm could be obtained. The worms selected for use were all seven, eight or nine mm in length and the total length of the worms in each group was found.

In order to insure a uniform diet, any food mixture given to planarian worms must be thoroughly blended. This led to the selection of brain tissue as the basic food, because its soft consistency after heating renders it capable of intimate incorporation with the liver extract. A paste was made from thin slices of the cortex of sheep's brain, the white matter being excluded as much as possible, and a portion of this was retained without further treatment to feed the control group. Then the rest was placed in a closed vial and immersed in boiling water for fifteen minutes. This was again mashed to an even consistency and a second experimental group was fed on this "heat treated" brain. A third group was fed upon "heat treated" brain which had been thoroughly blended with fresh ether extract of liver in the proportion 500 mg brain to 50 mg ether extract. In this way it was possible to compare the following foods as to their growth-promoting effects:

the worms fed upon heated brain tissue small E they were also quite thin and in a failing conditi while in the other groups the worms were fat a apparently prospering.

These experiments have been repeated with var tions with the same general results. In one ser the ability of cod liver oil to restore the damage de by heating the brain tissue was tried. Three dr of ordinary, commercial cod liver oil were added 0.5 gm of the heated brain tissue and the mixtu was fed to worms for a period of three weeks. T worms which received cod liver oil showed even L growth than those which were fed on heated bra tissue alone. All the mixtures used have been w taken by the worms. They advance to the vari foods quickly, and as far as can be judged by a pearances they eat as heartily of such foods as heat brain tissue mixed with cod liver oil as they do of raw brain tissue.

I have already shown that the growth-promoti power of liver for planarian worms is diminished the exposure of the liver to much lower temperatu than that used in the above experiments. The structive effect of heat is manifested with the use temperatures as low as 30°. The highly labile ch acter of the substance involved would seem to d ferentiate it from the vitamins with the except of Vitamin C, while the fact that Vitamin C is ether soluble would again place a division line tween the substance active in these experiments the highly labile C. Moreover, the vitamin rich liver oil can not restore the damage done for growth of planarian worms by the heating of br tissue.

What the heat labile constituent of certain tiss may be which is so necessary a factor for the gro of planarian worms is a question, but our exp ments tend to show that it can be extracted from tissue by ether. Osborne and Mendel' have app ciated the excellent growth response following addition to the diet of rats of small amounts of tain organized masses of cells, such as liver or ye and have recognized the possibility that there within the cells certain constituents of dietary imp tance which are at present unappreciated.

Further details of these experiments will be I lished later. The value of the planarian worm a subject for studies in nutrition has been demonstr and this laboratory is engaged in developing vari aspects of the field.

PHYSIOLOGICAL LABORATORY,

UNIVERSITY OF CALIFORNIA

ROSALIND WULZE

2 Osborne, T. B., and Mendel, L. B., Journal Chem., 1926, LXIX, 661.

VOL. LXV

APRIL 8, 1927

No. 1684

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AGRICULTURE AND MODERN

SCIENCE1

I FEEL a special sense of appropriateness in speaking on such a subject as "Agriculture and Modern Science" at Yale University. Much work in agricultural science has been carried on in Connecticut from pioneer days down to the present, largely under the leadership of Yale professors and investigators.

The earliest scientific paper on agriculture by a resident of the English colonies was that of John Winthrop, Jr., first governor of Connecticut, on the "Description, Culture and Use of Maize," read before the Royal Society in 1663. The Rev. Jared Eliot, of Killingworth, Connecticut, in the next century, is believed to have been the first American to publish a book on agriculture. Eliot, by the way, was a chemist. In 1764 the London Society for the Encouragement of Arts awarded him a gold medal for his process of making iron and steel from black magnetic sand.

Modern scientific study of agriculture in America may be said to have begun with John P. Norton, who undertook his duties as first professor of agricultural chemistry at Yale in 1847. Professor Norton, after making a promising beginning, died at the early age of thirty. His plans were carried to fruition by his pupil, Samuel W. Johnson, who held the professorship of agricultural chemistry at Yale for forty years, from 1856 to 1896. Professor Johnson is recognized as the father of agricultural research in the United States. The work which he did in the fifties as chemist of the State Agricultural Society in the analysis of fertilizers "for the information and protection of farmers" and the exposure of frauds attracted wide attention. As early as 1854 he advocated the establishment in this country of agricultural experiment stations and wrote: "What agriculture most needs is the establishment of its doctrines. . . . If agriculturists would know, they must inquire. The knowledge they need belongs not to revelation but to science, and it must be sought as the philosopher seeks other scientific truth."

Due largely to Professor Johnson's efforts the agricultural experiment station idea first took shape in the Connecticut station, which began its career at

1 Address of the secretary of agriculture, at Yale University, New Haven, Conn., March 28, 1927, at 8:15 P. M., under the auspices of the American Institute of Chemists.

Wesleyan University, at Middletown, in 1875. Professor W. O. Atwater, a former student of Johnson's, was made director. Professor Atwater laid the foundation of American scientific studies in human and animal nutrition. The station was incorporated as a separate institution in 1877 and moved to New Haven. Professor Johnson became director, and offices and laboratory were supplied by the Sheffield Scientific School.

Professor Johnson's contributions to agricultural science were many and valuable. "How Crops grow" and "How Crops feed" are agricultural classics. His influence in bringing science to bear on all the varied phases of agriculture was far-reaching.

The success of the Connecticut Experiment Station led other states to follow. Dr. Johnson was active in developing a wider interest.

Another movement which had an important bearing on the development of agricultural research was the establishment of the bureau, now the Department of Agriculture, and the land grant college system by congressional acts in 1862.

The Department of Agriculture from the beginning was planned to be a national research agency. It has been gradually developed along these lines until now it is the most extensive research agency of the kind in the world, expending for fundamental research bearing on agriculture in its larger aspects more than ten million dollars a year and employing more than a thousand trained investigators and in addition a corps of more than four thousand who assist in the work directly or indirectly.

In the development of the land grant colleges the needs for research as well as education were evident from the first. Research data on which to build a more scientific agricultural education were largely lacking. The earlier years of the colleges were therefore not impressive from the standpoint of accomplishment.

In 1887, largely through the efforts of the colleges, the Hatch act was passed. This recognized the joint responsibility of the federal and state governments for promoting agricultural research and provided $15,000 a year to each state for that purpose. This was later increased under the Adams act to $30,000, and recently under the Purnell act to a final total of $90,000 a year to each state. On the average, not counting buildings, land and overhead of that kind, the states provide in addition two or three times as much more.

The general supervision of the work on the part of the federal government devolves upon the Department of Agriculture through a special Office of Experiment Stations, provided by law for that purpose.

The closest cooperation has developed in practically every phase of the work.

The three acts mentioned have somewhat different objectives. The first, the Hatch act, was general in its terms. The Adams act was designed to develop more fundamental research. The Purnell act broadened the field to include economic, sociological and home economic studies. In the earlier years problems of production, control of disease and insect pests, introduction and development of improved varieties of crops and animals, studies of fertilizers and soil fertility, feeding and breeding of livestock were paramount objectives. To-day these are not less important, but problems of marketing, finance, transportation and other economic and social aspects of agri culture are dominant and require the same careful study and analysis that have been given to the production aspects.

There is also a difference in point of view between the earlier and the later work in agricultural research. In the early stages, agricultural science borrowed heavily from general science, the discoveries in which it endeavored mainly to apply to agricultural problems. Latterly, institutions for agricultural research have themselves become contributors to scientific discovery to a constantly increasing extent.

Examples of agricultural progress through research may be found in practically every science and every group of sciences.

In chemistry the classic example is the early work on fertilizers. The foundations of this branch of agricultural science were laid by such chemists as de Saussure (whose "Chemical Researches upon Vegetation" was published in 1804), Boussingault, who introduced exact field experiments with fertilizers in 1834, and especially Liebig, whose epoch-making book, "Chemistry in its Application to Agriculture and Physiology," was published in 1840. Liebig's book was the foundation of modern scientific agriculture. His work inspired J. B. Lawes in England, who first began the manufacture of calcium superphosphate as a fertilizer and founded the first agricultural experiment station at Rothamsted.

One of the most brilliant examples of the benefits which have been conferred by chemistry upon agriculture is the Babcock test for determining the butterfat content of milk. It won grand prizes at both the Paris and St. Louis Expositions. Babcock's invention, from the effect which it had in improving dairy herds, in securing the payment for milk and cream upon a fat percentage basis, in controlling the processes of manufacturing dairy products, and in regulating the purity of municipal milk supplies, has been of inestimable value to the American people,