53 
Development. — The embryo is swallowed, and after hatching enters a villus of the 
small intestine, where it transforms into a cercocystis, which in turn falls into the 
lumen of the intestine and becomes adult. 
Geographic distribution. —Egypt, England, Italy, Sicily, Russia, Germany, Ser- 
via, France, Austria, Denmark, Siam, Japan, Pennsylvania, District of Columbia, 
Maryland, South Carolina, Georgia, Texas, Brazil, and Argentina. 
Medical significance. — This parasite is more or less common, par- 
ticularly in children in warmer climates. Treatment: male fern. 
Prevention. —If a patient harbors this tapeworm he should not be 
allowed to sleep in the same bed with another person. Personal clean- 
liness, especially after defecation. 
Fig. 84. — Proglottids of Hymenolepis nana: a, showing ovary; b, containing eggs in course of forma- 
tion; c, gravid segment. Enlarged. (After Leuckart, 18G3, 39G, fig. 114.) 
Fig. 85.— Segment of Hymenolepis nana showing three testicles, two ovaries, etc. Enlarged. (After 
Leuckart, 188G, fig. 409a.) 
Fig. 86. — Egg of Hymenolepis nana as seen in fresh feces. Enlarged. (After Ransom, from Stiles. 
1903, 85, fig. 85.) 
Fig. 87. — Longitudinal section of the intestinal villus of a rat, containing cystic stage of dwarf tape- 
worm. Enlarged. (After Grassi A Rovelli, 1892a, pi. 3, fig. 25.) 
