326 



THE ANIMAL PARASITES OF MAN 



Hymenolepis nana frequently occurs in man ; it was, moreover, not 

 possible to infect rats with segments of Hymenolepis nana (of man). 

 Accordingly this form may represent an independent species, which, 

 however, like Hymenolepis murina, also omits an intermediate host. 



Hymenolepis diminuta, Rud., 1819. 



Syn. : Tcsnia diminuta, Rud., 1819 ; Tcenia leptocephala, Crepl., 1825 ; Tcenia 

 flavopunctata, Weinld., 1858 ; Tcenia varesina, E. Parona, 1884 ; Tcsnia minima, 

 Grassi, 1886. 



This species measures 20 to 60 cm. in length, and up to 3*5 mm. 



in breadth ; there are from 600 to 1,000 segments. The head is very 

 small (0*2 to 0*5 mm.), it is club-shaped and has 

 ^f^f^^ a rudimentary unarmed rostellum ; the neck is short ; 

 the mature segments are 3-5 mm. in breadth, o - 66 mm. 

 in length ; the eggs are round or oval. The outer 

 egg-shell is yellowish and thickened, with indistinct 

 radial stripes ; the inner embryonal shell (embryo- 

 phore) double, thin ; the outer layer is somewhat 

 pointed at the poles ; oncosphere 28 ^ by 36 /A. 

 Between the inner and outer shells is a middle 

 granular layer. 



Hymenolepis diminuta lives in the intestine of 

 rats Mus decumanus (the sewer rat), Mns rattus (the 

 black rat), and Mus alexandrinus, rarely in mice ; it 

 is occasionally also found in human beings. 



Weinland described it from specimens collected 

 by Dr. E. Palmer in 1842, in Boston, from a child 

 aged 19 months, as T. flavopunctata. A second case 

 relating to a three year old child, from Philadelphia, 

 was only reported in 1889 by Leidy ; a third case 

 was simultaneously reported of a two year old girl 



in Varese (T. varesina) ; and Grassi 



described another case relating to a 



twelve year old girl from Catania 



(Sicily). Sonsino and Previtera reported 



FIG. 228. Hy- 

 menolepis diminuta ; 

 scolex. Magnified. 

 (After Zschokke.) 



P'iG. 229. Hymenolepis diminuta ; two pro- 

 glottids showing testes (3), ovary and vagina. 

 Slightly enlarged. (After Grassi.) 



FIG. 230. Hymenolepis diminuta \ 

 egq; from man. (After Bizzozero.) 



