proved for a while, but died, however, later. He refers vaguely in his New York City lecture to an evidence, which at best must have been very inconclusive at this early period, that some hitherto unknown food elements must be present in a complete dietary. He refers to this in 1906 as follows:

But further no animal can live upon a mixture of pure protein, fat and carbohydrate, and even when the necessary inorganic material is carefully supplied, the animal still can not flourish. The animal body is adjusted to live either upon plant tissue or other animals and these contain countless substances other than the proteins, carbohydrates and fats. Physiological evolution, I believe, has made some of these well nigh as essential as are the basal constituents of diet; lecithin for instance, has been repeatedly shown to have a marked influence upon nutrition, and this just happens to be something familiar, and a substance that happens to have been tried. The field is almost unexplored, only it is certain that there are many minor factors in all diets of which the body takes account. In diseases such as rickets, and particularly scurvy, we have had for long years knowledge of the dietetic factor, but though we know how to benefit these conditions empirically, the real errors in the diet are to this day quite obscure. They are, however, certainly of the kind which comprises these minimal quantitative factors that I am considering. Scurvy and rickets are conditions so severe that they force themselves upon our attention, but many other nutritive errors affect the health of individuals to a degree most important to themselves, and some of them depend upon unsuspected dietetic factors.

If we analyze this statement we must admit that Hopkins showed unusual perspicacity at this early time. On the other hand, he showed no evidence that he knew to what class of substances these mysterious agents could be referred. His mention of lecithin, for instance, makes him attribute a particular rôle to already known substances that has been undoubtedly misleading. If we compare this statement of Hopkins of 1906 with the statement of Bunge of 1891, viz., "Mice can live well under these conditions when receiving suitable foods (milk), but as the above experiments demonstrate that they were unable to live on proteins, fats, carbohydrates, salts and water, it follows that other substances indispensable for nutrition must be present in milk besides casein, fat, lactose and salts," we must admit that Hopkins did not advance the question much since the work of Bunge.

As regards my own rôle in the vitamine field the only claims I can put forward are: (1) the recognition of the existence of several vitamines; (2) the right conception about the importance of vitamines

3 J. Ind. Eng. Chem., 14, 64, 1922.

4 Analyst, 31, 395, 1906.

for nutrition; (3) the first chemical study of vitamine B (1911), which unfortunately for the problem has not been improved on yet; (4) general stimulation of researches in this field through expressed ideas, experimental and summarizing work.

We come to the conclusion, therefore, that the discovery of vitamines can not be attributed to a single man. Among the pioneer workers in this field can be named: Bunge, Röhmann, Stepp, Eijkman, Schaumann, Suzuki and others. And the most that one can concede to Hopkins is that he was one of the pioneers. His distinguished services in the field of biochemistry and physiology (discovery of tryptophane, the chemistry of the muscle, the discovery of glutathion) together with his charming personality have made him, even without the title of discoverer of vitamines, one of the leaders in the biochemical world.

STATE SCHOOL OF HYGIENE, WARSAW, POLAND

CASIMIR FUNK

CITATIONS OF SCIENTIFIC LITERATURE

MAY I make a comment and ask a question with reference to the recent notes on citations of scientific literature that have been appearing in SCIENCE?

Furfey (February 26, 1926, pp. 231 f.) makes many excellent comments. To his remarks upon the use of "op. cit.," I should like to add the comment that, much as uniformity is to be desired, clarity is even more important. There is something to be said for footnotes, since they allow the author to add important but casual information and content where a parenthesis or a parenthetical digression would break the main thought. Where references are to be given in footnotes, then it becomes obvious that they should be immediately available. For an author or editor to insist on uniformity with respect to "op. cit." means that often the most careful scrutiny of many preceding pages must be undertaken to find references. Plainly in such a case the reference ought to be repeated. On the other hand, the page which makes numerous references to the same articles should certainly not have the reference repeated upon it. There might be some rule, like a rule to repeat the reference every four pages and to use "op. cit." otherwise, but in general it seems to me better to let good judgment prevail over reason, and to decide in Ms. when the precise reference can easily be found and when it will be lost among others. My plea here is against arbitrary uniformity by authors or editors.

My other question concerns the place of the date in a citation. Leffmann's (February 26, 1926, p. 231) and one of Merrill's (November 6, 1925, p. 420) instances place the date separately from the volume and pages. It seems to me to be much better for the date

to appear between the citation of volume and the citation of pages, because the nature of the datenumber nearly always distinguishes it from the smaller numbers for volume and for pages, and one does not then have to use bold-face type or ordinarily to print "vol." or "v." I remember, however, once bringing tears into the eyes of a librarian by suggesting that the pages be separated from their volume by the date. It seems so logical to follow this order and to make for so much greater clarity that I can not understand why bibliographical practice is ordinarily against it. Can any of the readers of SCIENCE tell me why the date should not be interpenetrated between volume and pages?

A UNIFORM, clear style for footnote citations is unquestionably desirable and no one is in better position to realize it than the editors of journals receiving contributions from a wide range of authors. These very same journals also have a wide range of readers to whom uniformity and fulness of citation will be a boon.

N The danger to be avoided in the systematization of ミニ footnotes is over-abbreviation. Certainly, Arabic numerals are preferable to Roman because of the greater ease with which they are read; but when it comes to using cryptic formulas such as PSBA, JAFL, BAMNH, PCAS, AJS, ACM, etc., in referring to publications, it seems that we sacrifice clarity for the sake of saving half a line of type and give many a reader a crossword puzzle instead of a clear citation. Ink and paper are cheap. Why not use enough of both to make footnote citations uniform, clear, unambiguous and understandable to every reader?

UNIVERSITY OF CALIFORNIA

E. W. GIFFORD

RAILROAD PASSES FOR SCIENTIFIC

WORK

WITH the development of scientific research, many field investigations are carried on. Since science is poor, it would be desirable to have railroad passes to further this work. This laboratory has made plans to investigate some of the results, on the human organism, of a surgical operation. Such work will have to be done in the field, necessitating travel for which we have no funds.

The Interstate Commerce Commission, which regulates the issuing of railroad passes, provides free transportation to "persons exclusively engaged in charitable or eleemosynary work." It makes no mention of the matter of scientific research. Evidently, scientific research is a question which the Interstate

Commerce Commission has not considered. Is scientific research charitable or eleemosynary? Possibly a large part of research might be so called since there is no remuneration paid to college professors carrying on such research as an extra load to teaching. The results of much such research evidently are bestowed gratuitously on succeeding generations.

This laboratory has approached one railroad and they express their willingness to donate a pass if they can be sure that such action will be within the law.

It seems that it would be desirable that this question be considered by men of science and some statement be made to the Interstate Commerce Commission in order that this latter body may take some action. HERBERT W. ROGERS

PSYCHOLOGICAL LABORATORY,
LAFAYETTE COLLEGE

SCIENTIFIC BOOKS

Mosquitoes of Surinam-A Study in Neotropical Mosquitoes. By C. BONNE and J. BONNE-WEPSTER. Royal Colonial Institute of Amsterdam, Department of Tropical Hygiene, 1925, 558 pp., 31 pl.

DR. BONNE for a number of years was government bacteriologist of Surinam. He and his talented wife, Mrs. J. Bonne-Wepster, greatly interested in all sanitary matters, conceived the idea as early as 1916 that they would make a careful study of the mosquitoes of that region, and the present fine volume is the result. It took many years in the course of its preparation and a number of years more to secure its publication. They began to correspond with the writers in the summer of 1916 and to send in specimens for identification. Later, in 1919, they came to Washington and spent some time in the National Museum studying the mosquito collections and familiarizing themselves with the methods used in the preparation of the fourvolume Monograph of the Mosquitoes of North and Central America and the West Indies, the final parts of which had recently been published by the Carnegie Institution. Although very appreciative of the opportunities given them in Washington and greatly pleased with the result of their work here, their thoroughgoing ideas led them subsequently to visit the British Museum and to make a careful study of the types of neotropical species which had been before Theobald's eyes when he wrote his elaborate Monograph of the Culicidae of the World. They then went to Holland and began the arrangements for the publication of their extensive work. A little later they returned to Surinam and continued observations, but have now gone back to Holland, where Dr. Bonne has been made director of the Laboratory of the Cancer Research Institute in Amsterdam.

The book before us is, fortunately for us, written in English. It is printed admirably in large, wellspaced type. It covers 558 pages and is illustrated by thirty-one plates carrying eighty-three figures. These figures are of hypopygial structures and larval details. The work is practically exclusively of a taxonomic character. It includes full descriptions of all the species found by the Bonnes in Surinam, except certain species of Culex, subgenus Choeroporpa and also gives short notes on all the other species of tropical America known to them. In spite of its rather strict taxonomic character, there are occasional interesting and important biological notes appended to the descriptions. We wish there had been more of these notes and that the authors had been able to insert a separate chapter on group habits and ecology. Although three pages are given to the habits of the yellow fever mosquito, it would have been extremely interesting had they included absolutely everything about this important species that came to their notice in their years of study in Guiana. Their account of the apparent spread of the species from the coast to the interior is suggestive and may be of significance in the consideration of the question of the original home of yellow fever and the mosquito that carries it. It is quite possible that from the sub-title of the book a misconception may arise as to its scope. It is in no sense a complete treatise on Neotropical mosquitoes. We think it would have been better if Dr. and Mrs. Bonne had confined themselves to the original title, "Mosquitoes of Surinam." Then the original and painstaking observations on those insects would have appeared without dilution. From the sub-title, "A Study of Neotropical Mosquitoes," one would expect a mention of all the recorded Neotropical forms. The authors surely did not intend this construction, since they had but little first-hand information from regions farther south. It results that there is much compilation, in which the original observations seem lost. Of course the new matter is still there, but it has to be delved for and seems fragmentary. Simply the mosquitoes of Surinam would have been a condensed and very creditable piece of work.

If under a natural misconception from the subtitle we were to consider the work as a compilation of Neotropical mosquitoes, it is very incomplete. To begin with, the authors were apparently frightened at the large number of small Culex of the group Choeroporpa, and they simply left them out. At least the species might have been listed and the probable synonymy, in the opinion of the authors, pointed out. There are forty-five species recognizably described in this group, of which our authors notice but fourteen. By restriction to the tropics and omission of these recently described, the list would naturally be reduced somewhat; but still the omission may be considered

serious. Other omissions are less important, but can be picked up here and there. They serve, however, to diminish the authoritativeness of the work as relating to the whole Neotropical fauna. Especially with the Sabethids, lack of personal acquaintance with the species has led to occasional repetitions, as with homotina, treated both as a Wyeomyia and a Goeldia. The Brazilian species described by Lutz and Peryassú have been omitted, as is stated. We think they should have at least been listed. Some day we shall find out what these species are; but with the specific criteria at present in use the old descriptions are worthless. We do not blame our authors for not going further; but we wish the work had been complete for the Neotropics.

But all this concerns itself with what might have been. We realize that the authors' work was done in Dutch Guiana, and that, as an account of the mosquitoes of Surinam, the work has a very high rank. With the exception of Panama, and excluding the work done in Brazil, we do not know of another tropical American region in which the Culicid fauna has been covered with the intelligence, care and completeness exhibited in this volume.

WASHINGTON, D. C.

L. O. HOWARD

HARRISON G. DYAR

SCIENTIFIC APPARATUS AND

LABORATORY METHODS

A SIMPLE METHOD FOR OBSERVATION OF THE LIVING CHICK EMBRYO

DURING the progress of a series of observations1 by the author on the effects of suffocation on the chick embryo, it became very desirable to know the exact time of the cessation of heart beat. It seemed to us that it should be possible to remove a portion of the shell, cover the egg loosely to reduce evaporation and observe the embryo as often as desired. We first tried removing about a fourth of the entire shell from the top of the egg when it was lying in a horizontal position, placing the egg on a piece of paper, covering it with a beaker or tumbler and placing the whole in the incubator. This method enabled us to observe embryos from their forty-fourth hour of incubation to about their hundred and twentieth hour. Eggs opened before the forty-fourth hour of incubation seldom developed further.

Then it was found that by removing about a square inch of shell from the large end of the egg, together with a little albumen, placing the egg in a vertical position in the neck of a short, wide-mouthed bottle, (simply for support in that position), and covering

1 Byerly, T. C., 1926, "Studies in Growth. I. Suffocation Effects in the Chick Embryo," Anat. Rec. vol. 32.

bottle and egg with a beaker just tall enough to clear the egg, the embryo would develop from the twentyfourth to the hundred and tenth hour of incubation. The embryo came into view at the edge of the exposed surface very soon after the shell was removed. Mortality was rather high.

Up to this time, we had been unsuccessful in developing normal embryos in eggs from which such an area of shell had been removed prior to incubation. But at this point we found that by retarding evaporation still further by plugging the tumbler or beaker used as a cover loosely with a towel or with cotton it was a very simple matter to observe approximately normal development in the embryo from the unincubated stage to about one hundred five hours incubation. These chicks die at a remarkably uniform age; they do not die from the direct effects of evapoiration. The causes of their death are being investigated in these laboratories at present.

This method makes it possible for any undergraduate student to study the first four days of the development of the chick embryo in the same chick, to catch any desired stage for histological study, and that without the mastery of a difficult technique or a supply of expensive apparatus. It is almost superfluous to point out the added ease of experimentation that this technique offers the investigator of the early developmental physiology of the chick embryo.

The materials required are: 1 tumbler, 6" x 2.5′′; 1 straight-side bottle, 3′′ x 1.5", and one small towel. The bottle and tumbler should be washed with 95 per cent. alcohol; further sterilization has so far been unnecessary. The towel should be crumpled and placed beneath the bottle containing the egg and all three inserted into the tumbler until the surface of the egg almost touches the bottom of the tumbler.

The as

scales.1 Later, a similar frothing of the cytoplasm in various cells was noted to occur with any plasmolytic agent after preliminary action of trivalent cations even in very dilute solution. In sufficiently high concentration, however, even the most innocuous plasmolytes by themselves may cause subsidiary vacuoles to arise in the cytoplasm-a matter of common observation.

It is not only with plasmolyzing agents that this effect is produced, but also with other more readily penetrating substances, e.g., narcotics such as chloroform and ether and by salts after exposure to very low concentrations (1 per cent.) of these. The outer surface and also the interior of the chloroplasts are common situations for the vacuoles to arise when produced in this way, as was observed even by von Mohl.

But without any artificial influence similar vacuoles may form in normal cells. One of us recently demonstrated their constant occurrence in the gametes during the conjugation process in Spirogyra3 and further proved their excretory function as exercised in the taking up of water from the central vacuole and its discharge to the exterior in typical "contractile" fashion. The same author has recently found Vampyrella to be comparable in a remarkable degree to the gametes of Spirogyra, in that rapid excretion of water takes place by the activity of numerous contractile vacuoles appearing anywhere in the hyaline zone of the body; and that in addition to water, solid excreta are ejected by the simultaneous action of small vacuoles dispersed beneath the entire free surface.

To this is now to be added two principal facts primarily observed by the other writer, but studied by both of us, viz., (1) that the vacuoles produced under the action of a strong plasmolyzing agent are also contractile, and (2) that these vacuoles originate from peculiar bodies already present in the cytoplasm. These bodies, more fully described elsewhere, bear a strong resemblance to the growths of lecithin in water which have long been known as "myelin forms." They are normally of irregular and varying shape and consist of an external lipoid (osmic acid reducing) film which is usually liquid and extensible, enclosing apparently a more aqueous interior which is usually in circulation.

On treatment with a rather concentrated plasmolyzing agent, e.g., 1M or .75M cane sugar, the irregular 1 Lloyd, F. E., and Scarth, G. W., "An Introductory Course in General Physiology," Montreal, 1921.

2 Scarth, G. W., "Adhesion of Protoplasm to the Cell Wall and the Agents which cause it," Proc. Roy. Soc. Can. Ser. II, 17: 137, 1923.

3 Lloyd, F. E., "Conjugation in Spirogyra," Trans. Roy. Can. Inst. 15: 129, 1924.

bodies round up into small spheres which soon begin to swell and behave actively as contractile vacuoles. Since a fresh vacuole frequently starts up where one has disappeared it is possible that the evacuated membrane of one condenses to form the primordium of another. There is good reason to believe that sugar in the above concentrations enters the cytoplasm, where, by some process that we do not understand, it is probably concentrated in the contractile vacuoles, the resulting swelling and bursting being explicable simply as osmotic and surface tension phenomena. When, owing probably to high viscosity of the external surface of the protoplasm induced, e.g., by chromates, etc., the vacuoles fail to burst, the cytoplasm becomes thickened into a foamy mass. There are suggestions in the literature that an origin of vacuoles from similar bodies may be the rule in widely different cell types. For example, the production of secretory vacuoles from the so-called "Golgi apparatus" in cells of the Epididymis as described by Nassonov and Ludford. Now in Spirogyra one phase of the polymorphic myelin growths answers every description of the "Golgi apparatus.' Mention may also be made of Bensley's account based on a study of fixed materials of the evolution of the central vacuoles in onion roots from a canaliculate system which might well be identical with what we have described in the living cell.

To summarize, in the origin of vacuoles a portion of the living protoplasm which is enclosed in a film of lipoid substance enlarges in volume by the intake of water. At what stage the diluted protoplasmic substance ceases to be alive or whether the central vacuole may be part of the living system thus becomes a question analogous to that of the cell wall. There are grounds, however, for regarding the limiting film as not altogether dependent on the life of the cell for some of its most characteristic behaviors. As regards its growth the resemblances to the physical growths of lecithin is remarkable, and as regards semipermeability the lining of the sap cavity, which gives a similar lipoid reaction, may retain this property long after the cell is dead. This has been known since De Vries's "Plasmolytischen Studien," but we have recently observed extreme examples of the fact. In cells "killed" by iodine with eosin the vacuolar membrane contracted in concentrated glycerine; thereafter for 8 days it underwent slow deplasmolysis retaining its smooth contour, and, for a part of the time, maintaining a high concentration of eosin, indeed much higher than on the outside. Recently we have noted that the tonoplast can retain its smooth contour also after sufficient treatment with osmic acid 4 Nassonov, D., Archiv. fur mik. Anatomie, 100: 1924. 5 Ludford, R. J., Proc. Roy. Soc. B. 98: 354, 1925. 6 Bensley, R. R., through Cowdry's "General Cytology," p. 343.

FRANCK and Cario1 have shown that energy may be transferred from photosensitized mercury atoms to hydrogen at low pressures. The behavior of the excited hydrogen leads these workers to conclude that the active gas is hydrogen atoms. Bonhoffer2 has made a study of the decomposition of ozone by photosensitized chlorine and bromine to determine a relation between the absorbed radiant energy. Rideal and Norrish have used the photosensitization of ozone decomposition by chlorine in a determination of the kinetics of the reaction between hydrogen and oxygen. Taylor and Marshall give the results of their work on the reaction of hydrogen atoms, produced by excited mercury atoms, with a variety of gases, including nitrogen. The hydrogen and nitrogen used was freed from oxygen. Mixtures of nitrogen with excess hydrogen when illuminated with resonance radiation in the presence of mercury vapor showed little or no change in pressure and the tests with Nessler's reagent at the close of the runs were negative. However, Noyes5 reports that ammonia is formed in mixtures of hydrogen and nitrogen by transference of excited energy from mercury atoms to the molecules of the above gases. In the report by Noyes we are not informed if special precautions were taken to remove oxygen except in his investigation using mixtures of hydrogen and nitrogen in contact with vapor of boiling mercury. In this case no ammonia was formed when oxygen had been removed from the gas mixture previous to its contact with mercury vapor. Dickinson by using the method of Franck and Cario for making atomic hydrogen has shown that excited hydrogen atoms combine with oxygen at 45° C. This work has been extended by Mitchell,' who finds that the rate of the reaction between illuminated hydrogen and oxygen in presence of mercury vapor depends upon the pressure of the oxygen; and also that this reaction is retarded in the presence of argon. In the conclusion, he suggests the possibility that the active hydrogen is not atomic. These investigations described above have been conducted largely at low pres1 Zeit. Physik., 12, 162 (1922).

2 Zeit. Physik., 13, 94 (1923).

3 Jr. Chem. Soc., 127, 787 (1925).

4 Jr. Physical Chem., 29, 1140 (1925).
5 Jr. Am. Chem. Soc., 47, 1003 (1925).

6 Proc. Nat. Acad. Sci., 10, 409 (1924).
7 Proc. Nat. Acad. Sci., 11, 458 (1925).