664 



SCIENCE. 



[N. S. Vol. XVII. No. 434. 



Pettenkoffer and his followers, a real rela- 

 tion did exist between ground water level and 

 typhoid. In no other case, so far as the au- 

 thors are aware, has the possibility of the 

 influence of temperature been escluded. This 

 varies inversely with the ground water and 

 directly as typhoid fever, and the seasonal 

 curve in many places may be more plausibly 

 explained by this than by variations in ground 

 water. 



Murchison was the first forcibly to call at- 

 tention to the importance of the temperature 

 factor. Plausible as the explanation appears, 

 it has not gained wide acceptance, and, as 

 stated by the authors, has been practically 

 ignored in Germany. In summing up this 

 subject, they say: "Although most observers 

 have noted a characteristic seasonal distribu- 

 tion of typhoid fever, others, including some 

 of those who have written most recently, have 

 denied the existence of such variations. Of 

 those who realized that the variations did 

 exist, a few sought an explanation in the 

 factor of temperature. Their views did not, 

 however, gain acceptance, as the evidence fur- 

 nished was insufficient; and the common view 

 among medical men and sanitarians has been 

 that the fall maximum of typhoid fever was 

 an unexplained phenomenon." 



Sedgwick and Winslow have attempted, by 

 careful collection and comparison of statistics, 

 to see whether the relation shown by Murchi- 

 son, Liebermeister and Davidson for a few 

 places could be demonstrated for a wider 

 field. They have, therefore, brought together 

 statistics of the monthly variation in tempera- 

 ture and the prevalence of typhoid fever for 

 thirty communities. These include the states 

 of New York and Massachusetts, the District 

 of Columbia, Baltimore, Boston, Charleston, 

 Chicago, Cincinnati, Denver, Mobile, New- 

 ark, New Orleans, New York, Oakland, Phil- 

 adelphia, St. Paul and San Francisco in the 

 United States; the city of Montreal in Can- 

 ada; the cities of Berlin, Dresden, Leipsic, 

 London, Munich, Paris and Vienna in Eu- 

 rope; the Empire of Japan, and the British 

 Army in India in Asia; and the cities of 

 Buenos Ayres and Santiago de Chile in South 

 America. Four continents and both hemi- 



spheres are thus represented, and a wide range 

 of climate. 



Monthly values for temperature and typhoid 

 prevalence have also been plotted on appended 

 plates in order to show graphically the rela- 

 tion of the two curves. 



An examination of the plotted curves shows 

 a remarkable parallelism between monthly 

 variations in temperature and typhoid preva- 

 lence. Of the thirty communities considered, 

 eighteen show the parallelism to be almost 

 perfect. Three other typhoid curves, those 

 for India, for Charleston and for New Or- 

 leans, rise with the temperature in spring, 

 and fall with it in autumn, but show a tem- 

 porary decrease in the disease during the 

 time of greatest heat. In these twenty-one 

 cases the connection between the two factors 

 seems too close not to indicate a vital rela- 

 tion. In northern cities the course of typhoid 

 is acute; in cities with more and more equable 

 temperatures the curve is progressively flat- 

 tened. 



In the northern localities the maximum 

 occurs in September and October; in southern 

 cities with a niilder winter it comes in August 

 or July. In the two cities of the southern 

 hemisphere (Buenos Ayres and Santiago)" the 

 curves of both typhoid fever and temperature 

 are exactly reversed. In the case of the trop- 

 ical and subtropical regions — India, Charles- 

 ton, New Orleans — it appears that the rise 

 with the temperature, after beginning in the 

 usual fashion, is cheeked by some other factor, 

 perhaps strong sunlight or extreme dryness. 

 In the case of the nine cities which show 

 more or less irregular curves, the authors call 

 attention to a factor much neglected by pre- 

 vious students of seasonal variations; i. e., 

 the necessity of discriminating between sharp 

 epidemic outbreaks and the slow succession 

 of isolated cases which characterize that con- 

 dition usually known as ' endemic' They lay 

 stress upon a distinction, vital to epidemiolo- 

 gists, which must be drawn between infection 

 which reaches a number of persons at once 

 through a single medium, as water or milk, 

 and the slower, more complex process by 

 which a disease passes from person to person; 

 the path of the contagious material being 



