convert it into "meadow land." It was here that the buffalo last lingered in Kentucky, a few of them having been seen here as late as 1818.

With the settlement of the country and the extermination of the large wild game, the trees, which still lingered along the major streams, and possibly, also, on the tops of the sandstone knobs which are scattered over the region, began in their turn to reclaim the ground from which they had been driven, until now it is so well wooded that a person traversing the region who was unacquainted with its history would naturally conclude that each farm he sees is but the expansion of a clearing won from virgin forest by the axe of the sturdy pioneer, as elsewhere in Kentucky and Tennessee.

ASHEVILLE, NORTH CAROLINA

ARTHUR M. MILLER

SCIENTIFIC BOOKS

Bodenablagerungen und Entwicklungstypen der Seen. By G. LUNDQVIST. Bd. II of Thienemann's Die Binnengewässer, 1927, 124 pp. 14 pl. Published by E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart.

FOR a number of years Swedish investigators have been studying the bottom deposits of lakes in southern Sweden and much interesting and valuable information has been obtained in these studies. The

present volume deals primarily with these investigations. The first part treats of the methods of obtaining samples, including descriptions and figures of the apparatus, with the chemical and microscopical methods of studying the material, and with the system of representing the results by diagrams.

These lacustrine sediments are deposited in thin strata and the annual deposit of pollen makes it possible to trace the history of the beds; in this way it has been ascertained that the period of time covered by them ranges from a few hundred years in some instances to a few thousand years in others.

The relative proportions of the component materials serve to characterize the different types of sediments and a key for their identification is given, together with a series of thirteen microphotographs illustrating them.

The sediments are deposited in the form of beds and there is usually a succession of these beds whose sequence is dependent upon the solubility of the chief constituent of the deposit. In some instances the deposits seem to be homogeneous throughout, but through age determinations and by microfossil analyses it can be readily shown that they consist of a series of beds. Several types of bed sequences are shown by means of diagrams. In addition to chemi

cal and biological factors, the character of the beds is affected by certain dynamic factors, such as wind, currents and exposure to wave-action. The final section deals with the regional distribution of lake types in southern Sweden. A bibliography of sixtynine titles is given.

Die Tierwelt der Unterirdischen Gewässer. By P. A. CHAPPUIS. Bd. III of Thienemann's Die Binnengewässer, 1927, 175 pp. 70 figs.

This volume deals with the animal population of subterranean waters, such as are found in springs and caves. There are three chief sections which consist of (1) general, (2) faunistic, and (3) biological parts. The general part treats of methods of collecting the fauna, the character of subterranean waters and the characteristic environmental conditions existing therein. The subterranean fauna is divided into three ecological groups, namely, (a) Troglobionte, (b) troglophile, and (c) troglozene forms.

The second part consists of a list of the fauna of subterranean waters together with notes regarding the various forms and their geographical distribution. Mollusca and crustacea furnish the largest variety of forms.

The third part, consisting of fifty pages, treats the morphological adaptations of this fauna and the influence of subterranean life on the various organisms; the effect on the eyes and other sense organs, on the color, size and breeding habits are discussed, together with the origin and age of this fauna and the effect of the glacial period upon it. The bibliography includes 194 titles.

MADISON, WISCONSIN

C. JUDAY

SCIENTIFIC APPARATUS AND LAB

ORATORY METHODS

THE SPIRALS WITHIN THE TERMITE GUT FOR CLASS USE

INSTRUCTORS in bacteriology often realize that it is not easy on many occasions to find a satisfactory source of spiral-shaped microorganisms for class use. The proper varieties of bivalves are not always available and when one has a sufficient number of these at hand, one can not be certain that one will find satisfactory spiral material within them. Many also have made it a habit to look over students in an endeavor to find a marginal gingivitis since this condition yields most beautiful fields for direct smear or for the dark field. Young people, however, show this disease in rather limited numbers.

One of us (S. F. L.) while making a study of the

DS

protozoan fauna of the termite gut1 some years ago was impressed by the fact that the intestinal contents of these forms contain immense numbers of spiral organisms. It then occurred to us that these insects might offer a satisfactory source of supply of spirilla for class use in bacteriology. Repeated dissections according to technique which follows showed that material both for smear preparation and for dark field was rendered abundant immediately and with ma's I spectacular results. The wide distribution of termites over the United States renders them readily available to laboratory instructors in many parts of the country and careful search will discover them in practically it all regions.

The termites of the United States which are favorhable for this use and which are common enough to furnish laboratory material over any considerable area belong to three genera: Termopsis Hagen, the commonest west coast termite; Kalotermes, several species of which are found in the southwestern, southern and southeastern states; and Reticulitermes, with d numerous species, which has an extensive range including the whole of the United States with the a possible exception of certain of the northernmost central states. In the Bay Region of California all three genera are present. Of these genera, Termopsis and Kalotermes live entirely in wood, the former in decaying wood, the latter in sound, but dead wood, such as stumps or dead parts of living trees, in telephone poles and, further south, in house beams. Reticulitermes lives in the earth from which it attacks sound wood. It is the cause of considerable economic loss due to its attacks on wood of buildings, etc.

er S

The genera have been named in the order of decreasing size and increasing difficulty of laboratory culture. The difficulties encountered in laboratory culture of the termites arise from the necessity of considerable humidity together with the susceptibility AM of the organisms to fungus attack. Termopsis, the largest of these termites, is also the hardiest. Living as it does in fungus infested wood it seems to have E developed a resistance to fungus attack. The simplest method of keeping laboratory cultures of Termopsis is by placing double cones of filter paper in finger 1 bowls set in battery jars or museum jars. The larger jar should contain half an inch of water and must be covered with a glass plate. After some time on the filter-paper diet the wood particles disappear from the intestinal contents, which makes it easier to make V smears. A more satisfactory arrangement for long is periods or for the other genera is a series of mason jars with rubber stoppers pierced each with two glass 1 Light, S. F., Univ. Calif. Publ. in Zool., 1926, xxix,

For th

19

150.

tubes connecting by rubber tubes with the other jars, one of which contains water. Here filter-paper cone may be used or, better still for long cultures, pieces of the wood taken with the colony.

The whitish-headed individuals (nymphs of Termopsis and Kalotermes, workers of Reticulitermes) contain the most luxuriant flora. When material is needed the termite may be placed on a surface and held quiet by a probe pressed gently on the thorax. The extreme tip of the abdomen is then seized in fine-pointed forceps and by a gentle continuous pull the intestine may be removed. When teased the contents escape, including wood or paper fragments, great numbers of Protozoa, and the microorganisms. The lumen is lined with a close coat of spirals. Teased pieces of it mounted in Locke's or physiological saline present a beautiful picture. The material thus obtained may be mixed with two or three drops of sterile physiological saline upon a microscope slide and from this smears may be made immediately. Following air drying, they may be fixed by heat and then distributed to the students. Ordinarily ZiehlNielsen carbol fuchsin diluted six to ten times with water gives a satisfactory stain. The finest results, however, are to be obtained with the dark field condenser using the fresh gut contents diluted somewhat with sterile physiological saline.

Beginning with Leidy the students of the Protozoa of the termite have noted the spiral organisms which abound in the gut. Leidy, in his first paper,2 spoke of the "spirillum” and later3 named it Vibrio termitis. Grassi and Sandias speak of spirilla in European termites. Dobell describes Spirochaeta termitis from Ceylon termites, which he identifies with Leidy's species. More recently they have been discussed both by Cleveland and by Damon. Thus, we make no claim that these observations are original with us. We do desire to call the attention of laboratory workers and instructors to the fact that there is a source of spiral material which is easily available here in the United States.

UNIVERSITY OF CALIFORNIA

T. D. BECK WITH S. F. LIGHT

2 Leidy, J., Proc. Acad. Nat. Sci., Philadelphia, 1877,

141-149.

3 Leidy, J., Jour. Acad. Nat. Sci., Philadelphia, 1881, viii (New Series), 425-447.

4 Grassi, B., and Sandias, A., Atti Accad. Gioenia Sci. Nat. Catania, 1893, vi (series 4), Mem. XII, and 1894, vii (series 4), Mem. I. English translation in Quart. Jour. Mior. Sci., xxxix, 245-315 and xl, 1-75.

5 Dobell, C. C., Spolia Zeylanica, 1910, vii, 65-86.

6 Cleveland, L. R., Quart. Rev. Biol., 1926, i, 51–60.

7 Damon, S. R., Jour. Bact., 1926, xi, 31–36.

A COVER-SLIP CARRIER

THE apparatus described below has been used for some time by the author for carrying numerous coverslips through the fixing, dehydrating and staining fluids. Its advantages are: (1) It carries many cover-slips at the same time. (2) It is easy to move from solution to solution. (3) It necessitates much less material in the end. (4) It gives a like treatment to every piece of tissue on the cover-slip.

It is a small glass cage with one side open for the slip to be inserted. This opening is closed by a glass rod. The shelves are made of glass prongs that do not quite reach the middle and are slightly tilted so as to drain to the main bars. A small handle surmounts the entire structure.

In moving from one solution to another the cage was rested on absorbent paper, thus allowing excess fluid to drain off. Small glass tumblers with ground glass tops were used for reagents.

RQD

Mr. Morgan, of Eimer and Amend, was extremely helpful in changing my design for a metal cage to a glass one and can give any necessary information. HUGH H. DARBY

NEW YORK UNIVERSITY

SPECIAL ARTICLES

ON THE CHANGE FROM THE CONVECTIVE TO THE SPARK DISCHARGE OF THE MUCRONATE ELECTRODE

Apparatus. This is the same as described in my last paper,1 E E' being the electrode discs (2 cm. in 1 SCIENCE, XLV, 1927, p. 448.

diam.) of the spark gap x of a small electrostatic machine. E' is provided with an axial tube leading to the interferometer U-gauge beyond U, for measuring the pressure of the electric wind from the needle point y protruding a little beyond E. S is the head of the micrometer screw by which y may be set in length until the pressure at U just vanishes and the convective discharge from E to E' (wind) breaks up into the pressureless spark discharge. If thereafter y increases but .1 mm., the pressure at U instantly becomes a maximum, and relatively enormous, as heretofore explained (see graph A). Hence the par ticular position of S in question may be called the critical set.

Observations. With the apparatus in this condition, I noticed (in the dark) that if the finger touched the set screw s of the post P, the strong electric wind E to E' immediately broke up into a hollow cylinder of sparks implying absence of all pressure at U. A faint brush was also usually seen at s' of the post P'. Removing the finger restored the wind and its pressure at U. At such times the cathode needle point, only, is faintly luminous. The experiment may, of course, be indefinitely repeated. On touching the anode at s the behavior is similar, but much less marked. Sparking is apt to persist for the fraction of a second after withdrawing the finger, evidencing a kind of inertia.

It seemed probable that the cause of this occur rence would be the increased capacity of the electrode E and I therefore installed apparatus hoping to detect a relation between the extrusion y of the needle point, and the capacity increment in question. This I was unable to do consistently, as all capacities from 3 x 10-6 m.f. to about 10-8 m.f. often seemed to be equally effective in changing the wind into a spark succession. The larger capacities, however, admitted of a larger range of needle extrusion y. After long sparking the phenomena often seemed to tire.

As very small capacities were needed, I provided } a set of rectangular proof planes p all about b=6 cm. long and of varying width a (see figure). These were made to touch the set screw s in succession.

The effect of this contact for a=2, 4, 5, 6 cm. was merely to produce momentary initial sparking, after which the wind pressure reappeared in spite of the presence of the plane. With a = 7 cm., however, the plane in contact at s was able to hold the spark suc cession permanently, provided the distance (see figure) exceeded about 5 cm. For small z, pressure again appeared. For a = 8, 9 cm., etc., the plane became more and more dominating, and for a = 10 cm.

i

S

b

a

- Ост. 08 -16 .24 .32 •40 48 hold the spark even for z < 5 cm. and it sufficed to touch the prime conductor of the machine with the proof plane anywhere, however remote. The finger contact was exceptionally effective, with the radiating glow at s'very marked. These data give the general character of the experiment. They will vary somewhat in different adjustments. When the proof plane approaches s, a small spark jumps across to it, and it may be argued that this is probably what initiates electric oscillation between E and E', and thus breaks up the convection current from E to E'. Moreover, a certain length of the stem between E and P seems to be needed, supplying adequate self induction together with the capacity, to insure permanence of electric oscillation.

20

In the presence of the proof plane, y must be increased to again initiate the convection current. To reproduce convection when the finger touches P, y had to be increased about .04 cm. After the removal of the plane, y must again be decreased to obviate convections; i.e., the apparatus eventually oscillates under its own capacity. The behavior is in a way similar to the sensitive flame in acoustics, in which a smooth column begins to oscillate if stimulated. Just why oscillation ceases when y is too long by almost infinitesimal amounts, I have not fully made out; but one is tempted to infer that the electric circuit in such a case is in a dead-beat, or a-periodic condition, with too much friction somewhere probably at and near the needle. From this viewpoint, to increase У is to increase the electric resistance of the circuit.

Incidental variations. The data which I have given refer to what may be called the normal (cathode) behavior of the machine and appurtenances. The pressure of the convection wind may then run up to over 600 × 10-6 atm. At other times, which occur incidentally, the convection is always intermixed with more or less sparking and winds not much exceeding 100 × 10-6 atm. in anodal pressure, may be the highest obtainable, while the critical extrusion (y) of the needle may be five times greater at the maximum pressure. There may be no cusps in the graph. This is a source of much confusion, for the clear cut evidence of one day may be negatived on the next. On such off days the effect of capacities, etc., is also varied. The spark succession is a brilliant line, not cylindrical, and there is often uncertainty as to the critical set of the needle electrode.

Three examples of y s graphs (s being the wind pressure in 10-6 atm.) obtained on consecutive days, the machine (as such) working equally well in each case, are given in the diagram. One observes that the graphs are displaced bodily, high s and low critical y here going together.

Later it was found (with double micrometer electrodes) that while the curve a is the true cathodal graph, curves b, c, are types of the corresponding anodal graphs and that passage from one to the other resulted from spontaneous changes of the polarity of the electrical machine. Furthermore, when the critical set of the cathode is sharply made, the proof plane, if charged negatively, need not touch the cathode conductor, but is active (as by induction) from distances up to 10 cm. on either side of the spark gap x. Pursuing this test, I then used the usual negatively charged hard rubber rod and found this capable of changing the quiet convection current into a spark succession from a distance of even half a meter in any plane or orientation above or below the spark gap and on either side of it. A positively charged glass rod, on the contrary, had no observable effect anywhere. This puts a new face on the phenomenon, particularly as the increment of field impressed at the spark gap by the hard rubber rod is relatively small at best, and may actually be reversed, since the rod acts equally well on both sides of the spark gap. Finally, while the anodal behavior is in general similar, the positively or negatively charged rod has no effect on it in any position. The emission of positive or of negative electrons is thus distinguished by an extrusion, y, 4 or 5 times larger in the former case.

BROWN UNIVERSITY, PROVIDENCE, R. I.

CARL BARUS

Data obtained with a number of varieties of several species of fruits have been utilized to indicate the average keeping period as affected by storage at 0° and at 18° to 24° C. The fruits were handled and observations made as previously described in other publications (Overholser, 1922; (with L. P. Latimer), 1924).

With the fruits stored, an optimum period and a maximum period was determined. The optimum storage period referred to the average number of days the fruit could be stored and upon removal possess good quality and marketability. The maximum storage period referred to the time beyond which it was unsafe to keep the fruit in storage, although it was still in fair to good condition, because of likelihood of loss of quality, softening of texture, susceptibility to rot organisms, tendency to wilting and rapidity of breakdown subsequently.

Three pickings of the varieties of each kind of fruit were stored, the first being made soon after the beginning of the commercial harvest period, the second about the middle, and the third picking shortly before the close of the commercial harvest period for the variety.

EXPERIMENTAL DATA

Data showing the relative effectiveness of 0° C. and 18° to 24° C. in delaying the senescence of varieties of pears, plums, peaches and apricots, are presented in Table 1. The intrinsic keeping qualities of the species of fruits studied are generally considered by growers and shippers to be about in the order named, with the pears as a rule possessing the longest period, and the apricots the least period of marketability.

1 U. S. D. A. Bur. Plt. Indus. Bul. 40 pp. 9-26. 1903. 2 Jour. Agr. Research 19: pp. 473-500. 1920. 3 Calif. Agr. Exp. Sta. Bul. 344. pp. 426-463. 1922. 4 Cornell Memoir 81, pp. 1-54. 1924.

TABLE I

THE RELATIVE EFFECTIVENESS OF TEMPERATURES OF 0° AND 18° TO 24° C. IN DELAYING SENESCENCE

Kind of

Fruit

OF SEVERAL KINDS OF FRUIT

Maximum storage

period (days)

Pears

52

6

147

Pears

52

6

16

Plums

21

3

65

Plums

21

3

2

Peaches 49 Peaches Apricots. Apricots... 29

DISCUSSION

It should be pointed out that the actual number of days before senescence varied greatly, depending upon the variety, even within a species, and varied somewhat for a given variety depending upon the maturity when harvested, the region where grown, the season and other factors. Of course, some varieties of a given kind would keep much longer and others much shorter periods of time than the averages given. Nevertheless it is believed that the data indicated the average difference in keeping qualities of the several kinds of fruits.

It should also be pointed out that certain varieties within a given species kept relatively long at 18° to 24° C. and comparatively short periods of time at 0° C. Furthermore, with other varieties of the same species the reverse was true. The deductions, therefore, apply only to the average response of the varieties of a given species as contrasted with the fruit of another species.

DEDUCTIONS

The pears, which had the longest period before the approach of senescence, kept about nine times longer at 0° C. than at 18° to 24° C. The plums, which possessed on the average the next longest period be fore senescence, kept about seven times longer at 0° C. than at 18° to 24° C. In a similar manner peaches kept six times and apricots only five times longer at 0° than at 18° to 24° C.

The data show that the effectiveness in retarding senescence of cold storage temperatures (0° C.) as contrasted with temperatures of 18° to 24° C. varied, depending upon the inherent keeping qualities of the species.