336 



SCIENCE 



[N. S. Vol. LIV. No. 1397 



The a scale representing the number of dollars 



paid. 

 The h scale representing the number of hours 



worked. 

 The c scale representing the number of men 



working. 



The quotient a/h will represent the hourly- 

 rate paid. The quotient a/c will represent the 

 amount paid per man. The quotient b/c will 

 represent the hours worked per man. 



The radiant lines starting from the point 

 of origin of the coordinate system are the 

 equations of lines which represent a constant 

 quotient. The location of the points given by 

 the actual values of the table with reference 

 to the radiant lines of each quadrant therefore 

 determines graphically the actual value of each 

 quotient. 



For example, in the sixth week we observe 

 the location of point 6 in the first quadrant 

 between a rate of $.70 and $.80 per hour 

 (actual value 300/400 = $.75). 



In the second quadrant (as connected by the 

 cycle line) the location of point 6 is between 

 $20 and $25 a week (actual value 300/14 

 = $21.42) and nearer to the $20 line. 



In the fourth quadrant (as connected by the 

 cycle line) the location of point 6 is near the 

 30 hours per week line (actual value 400/14^ 

 $28.57 hours). 



If a longer period and a greater number of 

 values are under observation, a moving aver- 

 age could be calculated and plotted in a simi- 

 lar way. There are a great number of data 

 which have a similar relation to each other and 

 may be presented and analyzed by this method. 



Furthermore empirical data obtained by ex- 

 periment may be subjected to this method and 

 a possible positive or negative correlation of 

 their respective movements determined. 



R. vo^f HuHN 



New York City 



THE AMERICAN PHILOSOPHICAL 

 SOCIETY 1 



The etiology, prophylaxis, and serum treatment 

 of yellow fever: HroEYo Noguohi. Leptospira 

 icteroides was first isolated in 1918 from cases 

 of yellow fever in Guayaquil; later the organ- 

 ism was obtained from yellow fever cases in 

 Merida, Yucatan (1919) and in northern Peru 

 (1920). The finding has also been confirmed in 

 Mexico by Dr. Perez-Grovas, who transmitted yel- 

 low fever from eases of yellow fever in Vera Cruz 

 in 1920 and obtained cultures. The most recent 

 confirmation has come from Dr. Le Blane of the 

 Eoekefeller Institute staff, working in Vera Cruz. 

 The killed cultures of Leptospira icteroides were 

 first used for protective inoculation against yellow 

 fever in Guayaquil in 1918, where 427 vaccinations 

 were carried out. The results were so encouraging 

 (the morbidity rate among vaccinated and unvaeci- 

 nated during the same period being 11 and 110 per 

 thousand, respectively) that a vaccine several hun- 

 dred times stronger has been made in large quanti- 

 ties and employed in Mexico and various Central 

 and South American countries, the total number of 

 non-immune persons reported vaccinated being 

 about eight thousand. The development of protec- 

 tion is slow, requiring about 10 days for comple- 

 tion, and persons exposed to yellow fever just be- 

 fore vaccination or immediately afterwards are not 

 protected by vaccination. Excluding such instances, 

 however, there has been no case of yellow fever 

 among the eight thousand vaccinated in the various 

 localities, while among unvaccinated persons during 

 the same period and in the same areas there have 

 been about seven hundred cases of the disease. The 

 use of vaccine furnishes a rapid method of elimina- 

 tion of non-immune persons from areas where yel- 

 low fever is epidemic. By the application of sani- 

 tary measures to eliminate the mosquito carrier and 

 vaccination in the meantime to cut off the supply 

 of non-immune material from the infected mos- 

 quito, a threatening epidemic of yellow fever in 

 Guatemala and Salvador in 1920 is reported to have 

 been checked within one month from the appearance 

 of the first cases, that is, before a second set of 

 cases had developed. The value of vaccination as 

 an emergency measure does not, however, minimize 

 the importance of the anti-mosquito operations, the 

 elimination of both factors — the non-immune human 

 being and the infected mosquito — being essential 



1 Abstracts of papers presented at the annual 

 meeting, Philadelphia, April, 1921. 



