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it is not ÜÍ the kind anticipated by this reasoning. My atten- 

 tion was hrst called to the facts last December by Dr. H. 

 Douglas Singer, Director of the State Psychopathic Institute, 

 at Kankakee. In the Peoria hospital, where the largest number 

 of our cases have occurred, statistical data were obtainable 

 from July ist, igoq, to September ist, i()ii, and the curve 

 showing the number of new cases in this hospital presents five 

 notably high points, each the culmination of a wave of increase, 

 in the period of two years and two montlis which it represents. 

 In the first of these two waves the twenty-one new cases of July 

 are followed by seventy-one in August, and this maximum by 

 thirty-seven, twenty-three, twelve, and three for the months 

 of September, October, November, and December respectively. 

 In January 1910 there was but one new case ; in February 

 and March there were none ; in April there was one ; and with 

 this a new wave started, reaching thirty- four new cases in June, 

 dropping to but four in July, and rising in a second, lower wave 

 of sixteen and fifteen in August and September respectively, 

 dropping thence to one in October and none at all until February 

 of the following year. 



The largest number of new cases occurring in 1911 was only 

 seven, in August, the next largest number coming in May, when 

 there were six, and the two crests of these waves being separated 

 by the low period of June and July with one and three cases 

 respectively. In a word, the two annual high points come in 

 either May or June of two of these years, and in August of three 

 of them ; while in the two years for which our records are vir- 

 tually complete, the first wave is the highest in i()io, and the 

 second is highest in iqii. 



I believed at one time that we might make out a relation 

 of succession between these separate waves of increase and the 

 adult periods of successive generations of Simulium, but as my 

 data accumulate this relationship becomes decidedly doubtful ; 

 and certainly these double pellagra periods cannot be con- 

 nected with any seasonal diftcrences in the abundance of Simulium. 

 If there were any causal relation between these two facts there 

 should be but one high pellagra period to correspond with the 

 single spring outrush of Simulium adults ; or if there were 

 another it should be much lower than the first. 

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