June 16, 1922] 



SCIENCE 



655 



The experiments in epidemiology, carried out 

 ■with Doctor H. L. Amoss, have been made with 

 an infectious disease arising among mice to which 

 the name of "mouse typhoid" has been given. 

 The bacilli inciting the disease are readily grown 

 outside the body and reproduce the natural dis- 

 ease when fed to healthy mice. The purpose of 

 the experiments, which have extended over three 

 years, is the elucidation of the factors responsi- 

 ble for the epidemic spread of disease among man 

 and animals. Hitherto these factors have been 

 sought chiefly by the analysis of records of dis- 

 ease and death in man; this study represents an 

 effort to obtain more accurate data through di- 

 rect observation of an epidemic disease purposely 

 induced in small laboratory animals. 



Fishes used in Guayaquil for mosquito control 

 against yellow fever: Gael H. Eigenmann. 



The carbonic acid of the hlood in health and 

 disease: Lawrence J. Henderson. 



Some recent experiments concerning the nature 

 of the function of the Icidney : A. N. Richards. 



The Biblical manna: Paul Haupt. The 

 biblical manna was manna-lichen mixed with 

 tamarisk-manna and alhagi-manna. The manna- 

 lichen (Lecanora esoulenta) was ground in 

 querns, or pounded in mortars, and mixed with 

 the honey-like drops exuding from the soft twigs 

 of tamarisks or with the exudation of camel's 

 thorns. After this mixture had been baked it 

 tasted like honey-cake (Exod. xvi. 31) or like 

 pastry baked in sweet-oil (Numb. xi. 8). In the 

 early morning the tamarisk-manna is like wax, 

 but it melts in the heat of the sun (Exod. xvi. 21). 

 The accounts in Exod. xvi. 14-36 and Numb. xi. 

 7-9 are inaccurate and embroidered. The an- 

 cestors of the Jews were at that time, not on the 

 Sinaitic peninsula, but in northwestern Arabia. 



The earth inductor compass: Paul R. Hetl 

 and Lyman J. Briggs. A model of the U. S. 

 Air Service earth inductor compass, as developed 

 at the Bureau of Standards, and to which the 

 societj' awarded its magellanic medal, was 

 shown and demonstrated. This instrument is de- 

 signed for use in aircraft, where the ordinary 

 magnetic compass is unreliable. The fundamental 

 principle of its action is not new, but no previous 

 attempts at the construction of a comjjass on this 

 principle have given satisfactory results. In the 

 Air Service model a revolving coil of wire is 

 installed in the rear part of the airplane, where 

 the magnetic disturbance from the engine is 

 negligible. Current from this coil is led by wires 

 to the instrument board, where, by an entirely 



new device called a dial switchboard, the pilot 

 can so arrange the electrical connections that an 

 indicating galvanometer before him will read zero 

 only when the vessel lies in the desired course. 

 An effective compensation for rolling and pitch- 

 ing is provided, and by the judicious use of iron 

 in the core of the coil the size of the instrument 

 is kept down sufSeiently to permit of its installa- 

 tion in the limited space available in an airplane. 



The age of the earth from the geological view- 

 point : T. C. Chamberlin. 



Age of the earth from the paleontological view- 

 point: John M. Clarke. The age of the earth 

 from the point of view of the student of the life . 

 upon it, can be expressed only in comparative 

 terms. The paleontologist has been accustomed to 

 accept without much debate the allotmer.ts of time 

 that astronomers and students of celestial mechan- 

 ics have been disposed to assign for its age as a 

 planetary body. Life could not have begun until 

 long after the earth had started on its individual 

 planetary existence. No one knows how long it 

 takes a species of animal or plant to acquire its 

 specific characters or to attain changes in char- 

 acters that would show the passage of one species 

 into another. Animal and plant life have grown 

 under all possible differences of physical sur- 

 roundings, and the rate of growth and change is 

 in direct relation to the environment. Some 

 animals have endured through geological ages 

 without change while others have developed 

 changes explosively. It is improbable that there 

 will ever be a basis for estimating how long it 

 takes or has taken for one species to pass into 

 another, or to estimate concretely the endurance 

 of the life of any single species. The beautifully 

 preserved fossils of the ancient life of the Cam- 

 brian Period which lies almost at the base of the 

 record of life as registered in the rocks, show 

 such perfection of anatomical detail and such an 

 advanced degree of specialization in organs and 

 functions, that though they stand near the very 

 threshold of the recorded panorama of Ufe, 

 their structure demonstrates that it has taken 

 uncountable ages for them to arrive at such a 

 high degree of specialization. In other words, 

 inasmuch as starts are slow and as the starting 

 point was the nuclear cell, the length of time 

 required in rising from the undifferentiated cell 

 by evolutionary processes to the extraordinary 

 animals of the very ancient Cambrian period 

 must have been vastly greater than all the time 

 that has passed since the Cambrian period to the 

 age of man. The same fact has been made very 



