April 24, 19ii:i.] 



SCIENCE. 



665 



different in each individual instance. The 

 term ' prosodeniic ' has been used to describe 

 this form of infection. Such prosodemic dis- 

 ease, they rightly consider, should be mainly 

 considered in the analysis of data bearing 

 upon seasonal prevalence. An epidemic must 

 always be looked upon as a perturbing ele- 

 ment. Curves based upon a small number of 

 cases will always be liable to show irregulari- 

 ties due to single epidemics, and this is the 

 explanation in four of the nine cities of their 

 irregular seasonal curves. In the case of the 

 other cities, the curves of which are based on 

 ample statistics — Chicago, Cincinnati, New- 

 ark, Paris and Philadelphia — the curves show 

 secondary maxima — one in December or Jan- 

 uary, the other between March and May. 

 These five cities draw their supply from sur- 

 face sources liable to gross pollution. Heavy 

 autumn rains and spring floods carry into 

 these surface water supplies a larger amount 

 of pollution than reaches them at any other 

 time. 



The authors generalize: Winter and spring 

 epidemics are characteristic of those cities 

 whose water supply is most subject to pollu- 

 tion; they are absent from communities which 

 use filtered water or water obtained from ade- 

 quately protected watersheds. They conclude 

 that wherever a sufficient niimber of cases 

 have been considered a direct relation between 

 typhoid fever and temperature appears to be 

 general and invariable. 



The probable mechanism of the seasonal 

 changes, according to their conception, may 

 be given in their own words : " The bacteri- 

 ology and the etiology of typhoid fever both 

 indicate that its causal agents can not be 

 abundant in the environment during the 

 colder season of the year. The germs of the 

 disease are carried over the winter in the 

 bodies of a few patients and perhaps in vaults 

 or other deposits of organic matter, where 

 they are protected from the severity of the 

 season. The number of persons who receive 

 infection from the discharge of these winter 

 cases will depend, other things being equal, 

 upon the length of time for which the bac- 

 teria cast in these discharges into the en- 

 vironment remain alive and virulent. The 



length of the period during which the microbes 

 live depends largely upon the general tempera- 

 ture; as the season grows milder, more and 

 more of each crop of germs sent at random 

 into the outer world will survive long enough 

 to gain entry to a human being and bear fruit. 

 The process will be cumulative. Each case 

 will cause more secondary cases, and each of 

 the latter will have a still more extensive 

 opportunity for widespread damage. In our 

 opinion the most reasonable explanation of 

 the seasonal variations of typhoid fever is a 

 direct effect of temperature upon the persist- 

 ence in nature of germs which proceed from 

 previous victims of disease." 



This paper on the seasonal prevalence of 

 typhoid fever merits a careful study in the 

 original, and, in the main, one familiar with 

 this subject must be impressed with the just- 

 ness of the conclusions based upon the data 

 there brought together. 



Philip Hanson Hiss. 



SCIENTIFIC JOURNALS AND ARTICLES. 



The April number of the Transactions of 

 the American Mathematical Society contains 

 the following papers : ' The approximate de- 

 termination of the form of Maclaurin's 

 spheroid,' by G. H. Darwin; ' On twisted cubic 

 curves that have a directrix,' by H. S. White; 

 ' Ueber Curvenintegrale im ?n-dimensionalen 

 Eaum,' by L. Heffter ; ' The generalized Bel- 

 trami problem concerning geodesic representa- 

 tion,' by E. Kasner ; ' On the holomorph of a 

 cyclic group,' by G. A. Miller ; ' Quadric sur- 

 faces in hyperbolic space,' by J. L. Coolidge; 

 ' Ueber die Eeducibilitat der reellen Gruppen 

 linearer homogener Substitutionen,' by A. 

 Loewy ; ' On the possibility of differentiating 

 term by term the development for an arbitrary 

 function Of one real variable in terms of Bes- 

 sel functions,' by W. B. Ford ; ' On a certain 

 congruence associated with a given ruled sur- 

 face,' by E. J. Wilczynski ; ' On the class 

 number of the cyclotomic number field 

 fc(e ■-"*'"),' by J. Westlund. 



The May number of the Bulletin of the 

 American Mathematical Society contains : 

 Report of the February meeting of the 



