88 



WILLETS. 



The percentages of persons infected with the various parasites are 

 given by years up to the seventh year for the purpose of calling attention 

 to the very high percentage of children, even infants, who harbor intestinal 

 parasites. The results obtained show that infants between 1 and 2 years 

 give an infection of 50 per cent with 59.46 infections per 100 examined. 

 A year later the percentages rise to 75 and 90.76, respectively. 



GEOGRAPHICAL DISTRIBUTION. 



An attempt was made to study the geographical distribution of the 

 infections among the thirty-three cabecerias of San Antonio. The per- 

 centages varied as follows: 



Table X. — Variation in the percentages of the parasites found at San Antonio 



according to cahecerias. 



Parasite. 



Mini- 

 mum. 



Maxi- 

 mum. 



1 

 Ascavis - 



Per cent. 



31.43 



22.06 



0.00 



0.00 



0.00 



I'er cent 



82.44 



81.00 



63.79 



5.56 



7.55 





Triehuris _ .. 



Oxyuris _ _ 



Txnia 





Since the cabecerias vary in population from 58 to about 300, it was 

 to be expected that there would be considerable variation in the per- 

 centages of the various parasites found. As a rule the lower percentages 

 were obtained in the smaller cabecerias; the higher ones in the larger. 

 This particularly was true in regard to the findings for Ascaris. The 

 occurrence of the hookworm seemed to be influenced chiefly by the nature 

 of the sites selected for houses. Where the homes were located upon a 

 rocky soil the infection with hookworms was less than where they were 

 upon the lowlands. Tor instance, in cabecerias 2, 18, and 26, which are 

 built on rocky soil, 23.60, 22.06 and 35.37 per cent were infected against 

 81.00, 70.59 and 67.09 per cent in cabecerias 14', 4 and 13, built on the 

 lowlands. Since women are not found in the fields as often as men, it 

 would be expected that a greater percentage of men would be infected 

 if the infection took place in the fields (lowlands). This was found 

 to be the case in the whole series (74.89 per cent against 52.83 per cent) 

 and in the representative cabecerias under discussion as shown below. 



