432 THE SCIENTIFIC MONTHLY
The prevailing system of plantation labor in the south is the negro tenant system^ and the prevention of malaria among the tenants is con- sidered the most important point in the problem of preventing the dis- ease on a plantation. In the tenant system, the family is the unit in contrast to the day-wage system, where the individual is the unit. The family was, therefore, made the unit in the study.
The figures in this paper are based on the conditions that obtained during the season of 1914. The survey work included a detailed study of the 74 tenant families on a plantation and the amount of malaria among them in a region where the plantation operations and endemic malaria are typical. The plantation cultivated 1,800 acres of land, 1,191 acres by the tenant system and 609 acres under the direct super- vision of the plantation management by labor drawn from the tenant families on a day-wage basis. The tenants averaged 16 acres per family. The 74 families show a total of 299 individuals, or an average of 4 per- sons per family.
The crops grown on the plantation consisted of 743 acres of cotton and 448 acres of com under the tenant system and 80 acres of cotton, 209 acres of corn, 200 acres of oa-ts, 70 acres of cow-peas and 50 acres of lespedeza hay under the day-wage system.
AH time was reduced to adult time or man days of labor. The time of a male over 18 years of age was figured as full time, a male from 12 to 18 years as one half adult time and from 8 to 12 years as one fourth. The time of a female was figured as one half the time of a male. No account was taken of the time under 8 years of age. Beducing all the available labor on the plantation to adult time, there is an equivalent of 2 adults to each of the 74 tenant families.
The actual time lost through malaria consisted of 970 days for those treated by the plantation physician, 487 days in those cases not report- ing to the physician, and 385 days lost by non-malarial members of the families in attending those who had the disease. There was a total loss of 1,842 days. This reduced to adult time, not taking account of illness in members of the families under eight years of age, amounts to 1,066 days of adult time from May to October, inclusive. The time lost aver- aged 14.4 adult days for each family. There were 166 cases of malaria in 138 persons out of the total of 299 members of the tenant families. There was a loss of time equivalent to 6.42 adult days for each case of malaria. The seasonal distribution of the cases of malaria was as fol- lows: May, 15 cases; June, 31 cases; July, 25 cases; August, 38 cases; September, 36 cases, and October, 21 cases. The number of adult days lost through malaria, then, is 96 days for May, 199 days for June, 161 days for July, 244 days for August, 231 days for September and 134 days for October.
The effect of loss of time upon the crops can be measured by the
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