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As in the case of his volume on the "Laws of Wages," Prof. Moore brings a distinct freshness of view to his task, and has made an important contribution to the subject with which he deals. What one most misses is any reference to the labours of others who have preceded him in the same field, and rendered the hypothesis one that many have already accepted, though some of them may only be willing to regard the weathercycle as a contributory cause.

Directions for a Practical Course in Chemical Physiology. By Dr. W. Cramer. Second edition. Pp. viii+102. (London: Longmans, Green and Co., 1915.) Price 3s. net. THIS is a useful little laboratory manual, in which the author states he has departed from the method usually employed. This departure may be illustrated by an example; there are certain tests for starch; it is usual to take commercial starch and perform the tests with this; the student is generally instructed also to prepare enough starch from the potato to illustrate its microscopic appearances. Dr. Cramer adopts the method of starting with the potato, and instructs his pupils to prepare from it enough starch for macroscopic experiments also. The distinction between the two methods is rather apparent than real, and Dr. Cramer's method involves more trouble to the student, which may not be a bad thing. Another departure one notices is that the results of a reaction are not explained; he interpolates instead questions such as, what change occurs? or why is this? or explain the result. This plan of stimulat

ing inquiry is an excellent one for the student | above the average; but one fears that 95 per cent. of the class will leave the questions unanswered, and be content with their ignorance. The author, moreover, is not consistent in the use of this method of questioning; one notes, for instance, in such subjects as blood-clotting and nerve chemistry, subjects on which Dr. Cramer holds special views of his own, that the teaching is didactic; it would evidently be unsafe to leave students here free to pursue independent inquiry.

W. D. H.

Soil Conditions and Plant Growth. By Dr. E. J. Russell. Pp. viii+ 190. New edition. Monographs on biochemistry. (London: Longmans, Green and Co., 1915.) Price 5s. THE first edition of Dr. Russell's book was reviewed in the issue of NATURE for October 24, 1912 (vol. xc., p. 215). To the new edition a chapter has been added on the relationship between the micro-organic population of the soil and the growth of plants, and also a number of sections dealing with recent developments of other parts of the subject.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Early Figures of the Opossum.

IN view of the fact that several communications have appeared in NATURE during the past year concerning the first mention of the American opossum in literature, it may not be inopportune to direct attention to some of the early illustrations of this animal in maps and in printed works. First of all, it should be stated that the earliest reference to the opossum is found in the famous collection of voyages known as "Paesi Novamente Retrovati," published in 1507. In chapter cxiii. of that work it is mentioned that a live specimen, taken by the Pinzons in Brazil in 1500, was exhibited in Granada.

In the Waldseemüller map of 1516 a drawing intended to represent the opossum, as indicated by its accompanying legend, is introduced in the Brazilian region of South America; and this figure is copied in a number of later maps, and also in the Italian edition (1558) of Sebastian Münster's "Cosmographia."

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FIG. 1.

Under the native designation of "Su," a grotesque figure of the opossum was given by André Thevet, in his volume published in 1558, and in the same year appeared the "Wahrhaftig Historia" of Hans Stade, of Homburg, wherein occur (cap. xxxi.) two illustrations, and descriptions, of these Brazilian animals, one of which is called the "Servoy (Didelphis marsupialis, L.) and the other "Dattu" (Dasypus novemcinctum). The descriptions read as follows:

"There is also a kind of game, called servoy, which is as large as a cat, and has a tail like a cat; its fur is gray, and sometimes grayish black. And when it breeds, it bears five or six young. It has a slit in the belly about half a span in length. Within the slit there is yet another skin; for its belly is not open, and within this slit are the teats. Wherever it goes, it carries its young in the pocket between the two skins. I have often helped to catch them and have taken the young ones from out of the slit."

"There is another sort of animal found in this country which the savages call dattu; it stands about six inches high and is nine inches long; its body is covered all over, except underneath, with a kind of armor. This covering is horn-like, and the plates overlap one another like those of chain armor. This animal has a very long snout, and is usually found on rocks. It feeds on ants. Its flesh is sweet and I have often eaten of it."

90

Several species of American marsupials are figured by seventeenth-century writers, such as J. E. Nieremberg (1635), George Marcgrav (1648), César de Rochefort (1658), and others. An illustration given by the last-named author is here reproduced (Fig. 1). C. R. EASTMAN.

American Museum of Natural History.

Differential Antiseptic Action of Organic Dyes.. AN important property of certain organic dyes is their differential antiseptic action. Thus, varieties of B. coli commonly met with in the intestine are more susceptible to the inhibitory action of the tetraethyldiamidotriphenylmethane derivative, "brilliant green," than are typhoid or paratyphoid bacilli. The use of a fluid culture medium containing this dye (along with telluric acid) facilitates greatly the isolation of scanty typhoid and paratyphoid bacilli from fæces, since the growth of the various members of the coli group can be restrained, while the organisms in question proliferate actively. The detection of cases of typhoid infection, e.g. in “carriers," which is frequently a difficult bacteriological problem, can be materially simplified by this procedure. But our supplies of brilliant green have hitherto been derived from Germany, and I shall be indebted to your readers for information as to whether this dye is prepared in a fairly pure state by anyone in this country.

C. H. BROWNING.

The Bland-Sutton Institute of Pathology,

The Middlesex Hospital, London, W.

The Physical Properties of Isotopes. DR. LINDEMANN (NATURE, March 4) deduces that the vapour pressure of lead from radio-active origin, or of radium D, should be very considerably different from ordinary lead at comparatively low temperatures. It would be no easy matter to test this at such a low temperature as 100° C. However, it is being found possible to make measurements of the vapour pressure of cadmium down to 10-6 mm., and the method should be applicable to the point in question.

It is interesting to note in connection with the last paragraph of Dr. Lindemann's letter that the arc spectra of lead of radio-active origin and of ordinary lead show no difference, as Mr. T. R. Merton has recently found, further confirming the view that the external electrons are responsible both for the spectra and the individual chemical properties of elements. ALFRED C. EGERTON.

19 Old Court Mansions, Kensington.

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TWO CHINESE TOURS.1

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A SOMEWHAT unexpected sequel to mission which Sir Francis Younghusband led to Lhassa in 1903-4 was the appreciation by Chinese officials of the fact that the trade in Indian opium, which has at times been held up as a reproach to England, was in reality due to the demand of China for the drug. It is interesting to reflect that the truth should first have dawned upon a Chinese envoy who had been educated in the United States. The novel idea took root and engendered a movement which spread in China with such rapidity that in 1906 an imperial edict dealing with the opium question This promulgated. rescript embodied elaborate provisions for the immediate curtailment and the gradual extinction of the use of the drug. Necessarily, therefore, it took account not only of the enormous Chinese out-turn of opium, but of the smaller, though still important amount imported from India. Proposals and counter-proposals were accordingly formulated in 1907 by the Governments of China and Britain, and certain regulations, to remain effective for three years, were agreed upon by the high contracting parties and became operative in 1908.

was

Meanwhile the Government of the United States thought fit to initiate a movement of an international character which culminated in the assembly at Shanghai in 1908 of an opium commission, the findings of which reflect a desire to aid the Chinese authorities in their crusade against the opium habit; while, before the preliminary period of three years had expired, negotiations for a new agreement between China and the United Kingdom were set on foot.

As

a preliminary to the ratification of this agreement it was desirable that his Majesty's Government should know what had been the actual effect in China of the restrictive measures adopted there in response to the imperial injunctions of 1906. The officer to whom the important duty of reporting upon this feature of the case was Sir Alexander Hosie. No one better fitted for the duty of traversing the six provinces of China, known to have been the chief opium-producing areas in that empire, could have been selected. Sir Alexander had already travelled extensively, and in some cases, as an officer of the Chinese Consular Service, had resided in the provinces 1 "On the Trail of the Opium Poppy. Opium-producing Provinces of China." Vol. i., pp. viii+300. Vol. ii., pp. 308. 1914) Price 25s. net 2 volumes.

2 vols.

A Narrative of Travel in the Chief By Sir Alexander Hosie. (London: G. Philip and Son, Ltd.,

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involved. During a sojourn of more than thirty years in China he had taken a keen interest in all the economic resources of the empire; he had, moreover, been one of the members of the International Opium Commission which met at Shanghai. The narrative and the results of the two official journeys, undertaken with the object of securing the information of which the British Government had need, are given in the volumes now before us.

As the author in his preface explains, the book is not devoted to the history of the opium question. Nevertheless, those interested in that question will do well to consult this work. The circumstance that such consultants may neither be inclined nor qualified to appreciate the whole of the contents has been forestalled by the provision, for their especial benefit, of a couple of appendices wherein the genesis of the anti-opium crusade is outlined, and the results of his own investigations of 1910-11 into the cultivation of the poppy are summarised.

made. But even when due allowance is made for this possibility, one of the most interesting impressions which the narrative of the author conveys is the extent to which species that are devoid of utilitarian interest and value have become eliminated. The naturally regenerated constituents of the woodlands on uncultivated mountain slopes appear in the main to be as strictly. economic as the species planted along highways and irrigation channels.

The detailed descriptions of the various stages should render the work useful to those who may follow the author's route, but the general reader will be most interested in, and will profit most from, the incidental accounts of the configuration, the industries, and the polity of the provinces traversed by him. A passage which excites interest and arrests attention deals with the famous Nestorian tablet at Hsi-an Fu in Shensi, while the temperate but convincing reference to the shortcomings of European cartography, the uniformity and simplicity of Chinese delimita

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FIG. 1.-The loss formation, with mule litter and passenger cart, Shansi. From "On the Trail of the Opium Poppy."

As compared with various other accounts of recent Chinese travel, an outstanding feature of the present work is the extent to which it deals with the conditions and the appearance of longsettled and closely cultivated portions of that empire. Having regard to the primary purpose of his two journeys this was inevitable, nor can the reader be too grateful to the author for the care and precision with which he recapitulates the various crops observed in the course of a particular stage. Even in districts where tilth is most intensive, however, areas occur which are unfit for cultivation, and are under timber. components of the vegetation in cases of this kind are as carefully assessed as the field crops. In one such passage the author warns the reader not to assume, because reference has been made almost exclusively to trees of economic importance, that species of less consequence were altogether absent. The same may be true of other stages, as to which no such reservation is

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FIG. 2.-Chinese ash (Fraxinus Chinensis) coated with insect white wax. From "On the Trail of the Opium Poppy."

tions and terminology notwithstanding, evokes the reader's sympathy. Space forbids more than a passing reference to a few of the interesting topics discussed in the work. Among these may be mentioned the cultivation of huskless grain, the use of the fibres quaintly known to European commerce as China jute and China grass, the preparation of varnish, the weaving of silk, the making of bamboo hats, the wood-oil industry, the smelting of copper, the mining of coal, the separation of salt, the planting of rice, the various contrivances for irrigation, the different types of bridges. With these and other equally interesting topics the reader may best be left to make himself acquainted by reading the book. One of the most interesting passages in the work deals with the familiar yet little understood loess formation (Fig. 1), so extensively represented in the area traversed during the author's northern journey. Another, taken from the southern journey, treats of the white-wax industry (Fig. 2),

for our knowledge of which we are mainly indebted to the author's powers of observation. These powers are so rarely at fault that it seems almost ungracious to indicate the only instance in which he appears to have been led into misapprehension; there is one passage in which what, from his succinct description, was obviously a silk-cotton tree has been confused with thatfrom a phytogeographical point of view-extremely interesting species, the tulip-tree of China. The book is admirably printed, and in its 600 or so pages we have noticed but one typographical

error.

THE TELEPHONE IN SURGERY.

IN N the Lancet of January 30 is published an address by Sir James Mackenzie Davidson, delivered before the Medical Society of London, on the telephone attachment in surgery. By this phrase the author refers to the attachment of a telephone receiver to a probe, or lancet, or other metallic instrument used by a surgeon when exploring a wound containing a bullet or other piece of extraneous metallic matter, in such a way that the sound heard in the telephone when the probe

comes into contact with the bullet enables the surgeon to make certain of the position of the

bullet in the wound.

As this matter appears to be of real importance at the moment to surgeons in the field hospitals of our armies abroad, we make no apologies for giving our readers a summary of the more salient features of Sir Mackenzie Davidson's address. His attention was first directed to the use of the telephone as an auxiliary in surgery thirty-two years ago, by the accounts of the attempts made by Graham Bell, to determine, by means of the induction balance, the position of the bullet in the body of President Garfield when he was assassinated in 1881. Speaking afterwards of these attempts, and of the difficulties attending the method-which had failed in that notable case to yield satisfactory indications-Graham Bell outlined another and simpler electrical method for the detection of bullets, as follows:

It consists of a telephone, to one terminal of which a fine needle is fixed, and to the other a plate of metal of the same nature as the needle. The plate is placed on the limb to be examined, and the needle is thrust in where the bullet is believed to be; and when it strikes the ball a galvanic battery is formed within the body. . . . This will cause a click to be heard in the telephone each time the bullet is struck. This is a far simpler apparatus than the induction balance, and one far more easily procured.

This method Sir Mackenzie Davidson tried in 1887 at the Aberdeen Royal Infirmary, in the case of a patient suffering from a revolver shot, using a silver probe joined by a wire to one terminal, and a silver plate, about 6 inches long and 4 inches wide, connected by wire to the other terminal of a telephone receiver. In subsequent years he employed the same method to verify the results of early X-ray localisations, and it enabled surgeons in the South African War to differentiate, as the

common probe could not do, between a distorted and broken up Mauser bullet and a fragment of bone. Sir Mackenzie Davidson states that until quite recently he took it for granted that the same metal must be used-as Graham Bell stated-for the probing instrument and for the plate placed upon the patient's skin. But since the outbreak of the present war the difficulty experienced by skilful surgeons in finding bullets in wounds, even after the most precise localisation by means of X-rays, has caused him to experiment further, and to extend the method. Briefly, he finds, as the result of experimenting on different pairs of metals, that there is nothing so satisfactory as a plate of carbon, such as is used in an ordinary bichromate cell, to place upon the moistened skin of the patient as the auxiliary pole. The surgeon's metallic instruments are usually of steel, often silver-plated or nickel-plated. The metals to be sought for are lead, iron (and iron alloys), copper, and nickel. Carbon presents a sufficiently wide difference in its galvanic properties from any of these to render it suitable. result is enhanced if the solution used to moisten the skin beneath the plate is the solution of iodine employed as a disinfecting agent, since iodine is also an excellent depolariser. A low-resistance telephone is better adapted than the more expensive high-resistance receivers used in wireless telegraphy, giving louder sounds besides being cheaper.

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The form of telephone recommended is one with double receivers fixed to a flexible steel hoop that is placed on the head, so that each ear listens to its own receiver, and is protected from extraneous sounds. The operating surgeon places the auxiliary carbon plate upon the patient's moistened skin at some convenient spot near the place where the foreign object is supposed to be situated, and it may be held tightly against the skin by bandage or plaster. If a bare wire of silver is used as probe, it should, of course, be properly disinfected. Or the wire may be wound round an ordinary probe or needle or forceps which is used, or a spring clip may be employed to connect the instrument to the wire connected to the telephone. No battery of any kind is needed, owing to the galvanic action between the carbon-plate and the metal of the bullet. If, under these conditions, the instrument is introduced into the body of the patient, it will on the first contact with the bullet or other metallic body cause a most unmistakable click; while if the probe or scalpel is gently moved along the foreign body so along the foreign body so as to make rubbing contact along it, an equally unmistakable rattling sound will be heard. Several examples of successful application, showing the advantages gained by the use of this method, are given by Sir Mackenzie, who states it to be his belief "that the time will come when no surgeon will attempt to remove a deeply embedded metallic body without having this telephone attachment at his command." He makes out an exceedingly good case for this application of the telephone to surgery.

The author's experience and ingenuity in applying X-ray methods to localise the position of foreign bodies are so well known that when he comes forward with improved methods of electric probing, which have the distinguishing merit of the utmost simplicity, we may be sure they will find immediate and extensive application.

GEODETIC SCIENCE.

[O. 3 of the new series of professional papers of the Ordnance Survey contains some excellent notes on the geodesy of the British Isles, by Colonel Close, R. E., which bring the position of geodetic achievement fairly up to date, and incidentally add some historical indications of the processes by means of which our position in the world of geodetic science has been secured. Their usefulness has been increased by the addition of a very ample bibliography of the science, and by simple diagrams illustrating certain special features affecting geodetic levelling, including the principal triangulation of Great Britain, the geographical position of the West European meridional arc, and of the European longitudinal arc. In the section of the pamphlet dealing with standard measurement it is interesting to observe that the national standard yard, which was legalised in 1855, consists of a marked length on a bronze bar bearing a definite relationship to the "international" metre (also a measured length on a bar), which was originally intended to represent one ten-millionth of the length of the earth's meridional quadrant.

Colonel Close's sketch of the various operations undertaken to determine the figure of the earth, dating from Airy's investigations of 1830 to Helmert's determination of 1906, proves incidentally the extraordinary value of the early investigations undertaken with inferior instruments. On Airy's figure the whole of the mapping of the United Kingdom still depends, nor have the results deduced from the reduction of the principal triangulation affected the map values. In the length of 700 miles from Shanklin to the extreme north of the Shetlands Airy's figure gives about four seconds in latitude too much, if we accept Helmert's figure as the criterion. This does not affect the linear accuracy of the map. Three figures were computed by Colonel Clarke (in 1858, 1866, and 1880 respectively) from the data furnished by the reduction of the principal triangulation. They are all in use, either in Africa or America. The mean value in length determined by Clarke of the semi-axis major of the ellipse, the revolution of which about its minor axis produces the spheroid of the earth's surface, is less than that of Airy and only slightly greater than that of Helmert. Colonel Close records his opinion that the probable value is somewhat greater than Clarke's mean.

Many people must have noticed the apparently haphazard way of recording "bench" marks by the Ordnance Survey to indicate altitudes determined by levelling. They are to be found on most un

substantial walls, on milestones, and even on gateposts, and they must, many of them, inevitably be unstable. In the section of the pamphlet dealing with levelling, Colonel Close indicates the method by which, in future, such marks will be rendered permanent. Concrete blocks will be sunk on to hard rock foundations at intervals of about twenty-five miles all over the country; a bolt of bronze, with a knob of flint being embedded in the concrete. This section is also of interest as a record of the difficulties experienced in dealing with the adopted datum of mean sea-level. Indian survey investigations have contributed largely to the solution of this troublesome problem. It is in India, too, under Colonel Sir S. Burrard, that the most comprehensive investigations have been made in the matter of the deflection of the level, and the apparent eccentricities of the force of gravity, including the difficult problems which beset the speculative subject of isostasy; but Colonel Close's references to early English methods of determining the value of deflection due to local topography are extremely interesting as a record of the first steps taken in the evolution of this special branch of geodetic science. These plain and intelligible notes on a highly complicated subject, being entirely free from any affectation of technical specialism, should attract a much wider range of scientific interest than is indicated by the title of Ordnance Survey Professional Papers. T. H. HOLDICH.

SCIENTIFIC FACTORS OF INDUSTRIAL

SUCCESS.

THE Institute of Industry and Commerce (now the Institute of Industry and Science), so the introductory leaflet states, is a counterpart of a German organisation known as the Hansa Bund. How the Hansa Bund arose or by whom and when it originated we have no knowledge. It is a confederation of important German firms for promoting, encouraging, and facilitating German home and foreign trade. It is proposed by similar means, but on somewhat "superior lines," to do the same for British industry, and the directors invite those interested in the development of our industries by the aid of science to enrol themselves as members. A portion of the revenue of each year is to be devoted to scientific research under the supervision of our most eminent men of science. Accompanying this leaflet are a number of brochures touching on the causes and effects of German commercial success and on 'the remedies for British commercial decline.

If "in the multitude of counsellors there is safety," in the diversity of their opinions there may also arise confusion. Sir W. Ramsay conceives that the main purpose of the Institute is to combat German industrial methods, which are said to be organised on a policy of dishonesty and trickery. This is to be undertaken by the State by adopting something of their methods, or by endeavouring to thwart them. Mr. S. Roy Illingworth, in his pamphet on "The Organisation

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