26 
factors, or perhaps of some one factor, which exert their effect par- 
ticularly in warm weather. 
The cases definitely attributed to infection in milk were not dis- 
tributed uniformly in regard to these seasons for the three years. 
They were as follows : 
Year. 
Onset of cases. 
Number of 
cases. 
1908 . 
September 24 to October 24 
52 
1907 
June 8 to August 17 
28 
fJuly 16 to August 20 
35 1 
1900 
< July 30 to August 13 - 
12 
79 
[October 2 to October 21 
32 ] 
It is interesting to note that there was a marked difference in the 
prevalence of the disease among the white and the colored races for 
the warm and cool seasons of 1908 and 1907. 
In 1908 there were reported in the cool season (January, February, 
March, April, May, October, November, and December) 449 cases, 
of which 95 were coloi-ed (cases to population, 0.97 per 1,000) and 
354 white (cases to population, 1.46 per 1,000), ratio of colored to 
white being 1 to 3.7. 
In the warm season (June, July, August, and September) of 1908 
there were reported 487 cases, of which 167 were colored (cases to 
population, 1.71 per 1,000) and 320 white (cases to population, 1.32 
per 1,000), the ratio of colored to white being 1 to 1.9. 
In 1907 there were reported in the cool season 451 cases, of 
which 98 were colored and 353 white, ratio of colored to white being 
1 to 3.6. 
In the warm season of 1907 there were reported 494 cases, of 
which 112 were colored and 382 white, ratio of colored to white being 
1 to 3.4. 
It appears from these figures that there was little difference in the 
ratios of colored to white cases for the two seasons of 1907; but if 
that year is divided into periods— -one including the eight months 
January, February, March, April, May, June, November, and De- 
cember and the other the four months July, August, September, 
and October — there is a marked difference, in the ratios for these 
two periods. 
Thus, in the former (cooler) of these periods there were reported 
58 colored cases (cases to population, 0.6 per 1,000) and 281 white 
cases (cases to population, 1.2 per 1,000), the ratio of colored to 
white being 1 to 4.8. 
In the latter (warm) of these periods there were reported 155 col- 
ored cases (cases to population, 1.61 per 1,000) and 454 white cases 
