Great improvements have been made in the effectiveness of the absorbent materials used in the canisters, and this, in turn, has increased several fold the general efficiency which it was possible to attain at the time when the manufacture of the masks was first undertaken, and hence to diminish the amount of material to be placed in the canisters. The significance of this will be understood when it is realized that there is a considerable friction to overcome when the inhaled air is drawn through the canister. This was so great in the earlier masks, that it made necessary a suction on the part of the wearer of the mask equal to that required to raise a column of water in a tube to a height of six inches; an effort not incomparable with that made by many asthmatic sufferers to draw air into the lungs. This frictional resistance has been materially lessened by the improvement in the protective materials, and every reduction, however slight, is a great boon to the troops. The materials used in the canisters are selected to react with gases of an acid character, and with those capable of destruction by oxidation, a process like that generally known as combustion. Much reliance is, however, placed upon the absorptive power toward gases exhibited by many porous substances, notably, high grades of charcoal. The principle is the same as that utilized in the "charcoal filters" sometimes attached to our faucets to clarify water supplies.

Of late a new problem has been presented, because of the use of gases in the form of "smoke-clouds," which easily pass through the protective materials contained in the canisters. This has necessitated the addition of another filtering medium, and has necessarily added somewhat to the resistance to be over

come.

How serious this "neutralization" of troops through the continuous wearing of masks may be, is illustrated by the condition which obtained before one of the recent violent attacks on the Western Front. It has been stated that the enemy fired gas-shells (mainly mustard-gas) at the rate of two hundred thou

sand shells per day for four days, each shell probably averaging about five pounds of material. While the gas-masks will protect the wearer from the inhalation of this gas, they must have required one or more renewals during this period. This attack was followed by a smoke-cloud attack which necessitated the use of the extension filters, thus subjecting the troops to added labor in breathing, after days of constant use of the mask. The physical strain under such conditions can not fail to have been severe. It is not, however, to be supposed that the enemy was allowed to spend his time in full comfort.

As a means of detecting the approach of a toxic gas, canaries and white mice are placed in the trenches, as they are peculiarly sensitive to these chemicals and show signs of distress from dilutions which are unnoticed by man, especially when the gases are nearly odorless.

Of the offensive side of this gas-war it is obvious that little can properly be made public. There is reason to believe that our Amercan chemists are making valuable contributions in this field.-Henry P. Talbot in the Atlantic Monthly.

SCIENTIFIC BOOKS Agricultural Bacteriology. By W. H. CONN. Third edition, revised by HAROLD JOEL CONN. Philadelphia, P. Blakiston's Son & Company. 1918. Pp. x+357. Illustrated. with 63 figures. $2.00.

The first part of the book is taken up with a discussion of the general characters of microorganisms and their rôle in the decomposition of organic matter. The second part, which occupies practically one fourth of the volume, is devoted to the relations of bacteria to soil fertility. The cycles of carbon and nitrogen are presented. This section includes a chapter on 'The Manure Heap and Sewage" and on one "Bacteria in Water." In the latter the rôle of water in the distribution of disease-producing organisms is discussed. The third part presents the relation of bacteria to milk and to butter and cheese.

The use of microorganisms in industrial processes directly related to agriculture as in the manufacture of alcohol and of vinegar, the preparation of sauer kraut and silage, and in the retting of flax is discussed in the fourth part.

The fifth part includes a chapter on resistance against parasitic bacteria. Tuberculosis is discussed in some detail. Only fourteen pages are devoted to the other transmissible diseases of animals and fifteen pages to the parasitic diseases of plants.

The last part presents 39 laboratory exercises designed to supplement the text.

The second edition was marred by many mistakes, both in fact and statement. Many of these have not been corrected in the present edition. Errors in fact are illustrated by the statement that ordinary soils contain 0.1 to 0.2 per cent. of nitrate (p. 53); that H,S may unite with water to form sulphuric acid (p. 78); that the sulphur appears within the cells of sulphur bacteria as minute reddish dots, and because of the color produced by the sulphur the bacteria are frequently called the "red bacteria" (p. 124). In fact the reddish color noted in some of the sulphur bacteria is not due to sulphur but to a pigment, purpurin. If the red color were due to sulphur, all bacteria that store sulphur would be red. Such is not the case.

It is stated that any product that contains much sugar is more likely to undergo alcoholic fermentation than putrefaction. A true statement as far as it goes, but likely to create confusion in the mind of the student, for a product containing much sugar practically never undergoes putrefaction and an alcoholic fermentation only when the product is so acid as to prevent bacterial development. In sugar containing liquids, the reaction of which will permit bacterial growth, an acid fermentation is constantly noted as in milk, maple sap, beet juice, etc.

The construction is often loose and in error, one part of a sentence being written in the present tense and another in the past, e. g., "But the bacteria which are isolated from such soil by ordinary methods showed no

power of nitrification" (p. 65). Errors in spelling are frequent, e. g., volitization (p. 80), seradella (p. 112), urase (p. 60).

An example of the use of an incorrect word is found on page 63 where it is stated that "The addition of another atom of nitrogen to the nitrate, giving a nitrate," etc. The formulæ used in this connection are correct.

The reader of the present volume will find the essential facts concerning the relation of microorganisms to agricultural processes presented in a most interesting manner.

UNIVERSITY OF WISCONSIN

E. G. HASTINGS

BIRTH STATISTICS IN THE REGISTRATION AREA OF THE UNITED STATES: 1916

IN the recently established birth-registration area of the United States-comprising the six New England states, New York, Pennsylvania, Maryland, Michigan, Minnesota and the District of Columbia, with an estimated population of 33,000,000, or about 32 per cent. of the total population of the United States-818,983 infants were born alive in 1916, representing a birth rate of 24.8 per 1,000 of population. The total number of deaths in the same area was 486,682, or 14.7 per 1,000. The births thus exceeded the deaths by more than 68 per cent. For every state in the registration area, for practically all the cities, and for nearly all the countries, the births exceeded the deaths, usually by substantial proportions. The mortality rate for infants under one year of age averaged 101 per 1,000 living births. The foregoing are among the significant features of the report. "Birth Statistics in the Registration Area of the United States: 1916," soon to be issued by Director Sam. L. Rogers, of the Bureau of the Census Department of Commerce, and compiled under the supervision of Dr. William H. Davis, chief statistician for vital statistics.

The birth rate for the entire registration area fell below that for 1915 by one tenth of 1 per 1,000 population; while the death rate exceeded that for 1915 by seven tenths of 1 per

1,000. The excess of the birth rate over the death rate for 1916, 10.1 per 1,000, was thus a little less than the corresponding excess for 1915, which was 10.9 per 1,000. If the birth and death rates prevailing in the later year were to remain unchanged, and if no migration were to take place to or from the area to which they relate, its population would increase annually by about 1 per cent. This rate, compounded for a decade, would yield a decennial increase of a little more than 10 per cent., or about half the rate of increase in the population of the country as a whole between the last two censuses, 21 per cent.

Of the total number of births reported, 799,817, or 24.9 per 1,000, were of white infants, and 19,166, or 22.8 per 1,000, were of colored infants. The death rates for the two elements of the population were 14.5 and 24.4 per 1,000, respectively. The deaths reported for the colored races (comprising all nonwhites) thus exceeded the births reported; but it is probable that the registration of births is less nearly complete among the colored than among the white population, and that therefore the rate shown for the former class is too low, whereas in the case of death rates there is probably not so great a margin of error.

Some indication of the fecundity of the native and foreign elements of the population may be obtained from a comparison between the proportion which the number of white foreign-born mothers formed of the total number of white mothers to whom children were born in 1916, and the proportion which the white foreign-born married women, aged 15 to 44, formed of the total number of white married women of corresponding ages in 1910.

From the table following, it appears that many more births occur to white foreign-born women, proportionately to their number, than to native women. In Connecticut, approximately 46 per cent. of white married women aged 15 to 44 in 1910 were of foreign birth, but about 62 per cent. of the white mothers to whom children were born in 1916 were natives of foreign countries.

The infant-mortality rate-that is, the number of deaths of infants under one year of age

per 1,000 born alive-throughout the registration area as a whole was 101 in 1916, as against 100 in 1915. This is equivalent to saying that of every ten infants born alive one died before reaching the age of one year. Among the 11 states these rates ranged from 70 for Minnesota to 121 for. Maryland; and for the white population separately the lowest and highest rates were 69 for Minnesota and 115 for New Hampshire. The high rate for the total population of Maryland was due to the presence of a larger colored element in that state than in any of the others, the rate for the whites alone being only 101.

The infant-mortality rates vary greatly for the two sexes and for the various nationalities.

With an infant-mortality rate of 101 for the registration area as a whole, the rate ranges for white children from 68 where mothers were born in Denmark, Norway and Sweden, to 148 where mothers were born in Poland, while negro children have a rate of 184. The range of rates among white males is from 74 for children of mothers born in Denmark, Norway and Sweden, to 171 for those of mothers born in Poland, while negro males have a rate of 202. The corresponding rates for females were 62, 124 and 166, respectively.

The following table shows, for the birth-pegistration area, by states and by cities having more than 100,000 inhabitants in 1910, the number of births in 1916, the per cent. of ex

cess of births over deaths, and the infant-mortality rate. Figures for the white and colored

EXCESS OF BIRTHS OVER DEATHS, AND INFANT MOR

TALITY: 1916

elements of the population are shown separately for those areas in which colored persons constitute more than one tenth of the total population.

SPECIAL ARTICLES

NOTE UPON THE HYDROGEN ION CONCENTRATION NECESSARY TO INHIBIT THE GROWTH OF FOUR WOOD-DESTROYING FUNGI1

THE importance of hydrogen (and hydroxyl) ion concentration as a factor in physico-chemical and biochemical studies of living organisms is being recognized. A careful study of this factor has not been made heretofore due largely to the lack of ready means for making the determinations. The indicator method was not seriously developed until about a decade or so ago, and the hydrogen electrode was not applied to such problems until recently, due partly, undoubtedly, to the fact that biologists did not realize its possibilities.

Consequently no exact information is at hand concerning the behavior of fungi, in general, toward varying degrees of hydrogen ion concentration. This remark applies especially to wood-destroying fungi. Information which is available is usually given in a rather vague manner with the use of such terms as alkaline," ," "slightly acid," "strongly acid" or as percentage of acid (or base) added.

The expression, P, is now widely used as a means of stating hydrogen (or hydroxyl) ion concentration. The term is used and explained in the literature sufficiently often to make its explanation here unnecessary.

The four fungi studied in this investigation are: Lenzite sepiaria, Fomes roseus, Coniophora cerebella and Merulius lachrymans. Synthetic and malt extract media were used. The data obtained showed that their growth is not inhibited until a surprisingly

1 This note is a brief statement of the results presented in a paper on the same subject in partial fulfillment of the requirements for the degree of Ph.D. at the New York State College of Forestry at Syracuse University. A considerable part of the work was done in the office of Forest Pathology, Bureau of Plant Industry, at the Forest Products Laboratory, Madison, Wis. Detailed data will be published soon.

high hydrogen ion concentration is reached, and furthermore, that these four organisms respond in about the same way, though there are distinct variations among them. Furthermore, as might be expected, the curves obtained are similar to those showing the relation between enzyme activity and hydrogen ion concentration.

H

The most important facts to be presented here can be shown by means of a general curve setting forth the general behavior of the four fungi studied. The curve shown in the accompanying figure is constructed by plotting as ordinates the weights in grams of mycelium, produced in about five weeks' time upon media of varying P values as represented by the abscissae. This curve shows in a very general way the mean of the individual curves for the different fungi when grown upon the two media. The weight of mycelium produced shows large variation among the individual curves while there is rather close agreement in the P values which are physiologically imH portant to the various fungi.

H

In the following discussion we shall speak of the "first critical point," meaning the P1 at B (figure), the point where the first marked deflection in the growth curve appears; the "second critical point," meaning the PH at C, where the second marked deflection in the opposite sense occurs in the growth curve; and the limiting acidity," meaning the РH at D, where practically no growth occurs. By "critical range" we shall mean the range of the P values included between the first and the second critical points.

H

The curve in the accompanying figure is drawn with the portion AB horizontal. In the individual curves-that is for a single fungus on a single medium-this part may be horizontal or may slope either up or down in passing toward B. Or again, in passing from A toward B the curve may rise to a maximum and then fall toward the critical point B where a sharp inflection downward occurs. Such a maximum, when present, usually occurs nearer B than A-that is, at a РH of about 3.0. The critical points stand out more sharply in some than in other curves and the first critical

individual curves. In some cases the line between these two points is nearly vertical. In this curve the point D appears as a rather abrupt point. Point C often occurs nearer the lower axis and the portion of the curve CD occurs more nearly horizontal with a more or less uncertain termination. However, the limiting PH value appears to be in the region of 1.7.

Translating these data into terms of normality, the first critical point occurs at about 1/350 normal, and the limiting acidity at about 1/50 normal, hydrogen ion concentration.