25 
All of the forms found in man are usually referred to simply as 
members of the genus Taenia , as Taenia solium , Taenia saginata , etc. 
Difficulty is occasionally experienced by physicians in determining 
tapeworms when they have only a part of the parasite for examina- 
tion. To meet the difficulties which thus arise, the following key is 
prepared : 
KEY TO THE SPECIES a OF TjENIA FOUND IN MAN. 
(For species known to occur in man in the United States, follow roman type.) 
1. Strobila 
Head 
Segments l 
Mature segments (namely, with genital glands) 
Gravid segments (namely, with eggs) 
Source of infection 
2. Strobila attains: 
2 to 3.5, rarely 6 to 8 meters in length; head armed; cosmopolitan 
T. solium (p. 
4 to 10 meters in length ( T saginata and T. confusa) 
1.4 meters in length; head unarmed; Africa T. africana (p. 
unknown length; original immature specimen measured 70 mm. long; head 
unarmed; Asiatic Russia T. liominis (p. 
0.5 to 2 meters in length; head armed T. pisiformis (p. 
0.15 to 0.6 meters in length; head armed T. tenrseformis (p. 
3. Head: 
armed with hooks (subgenus Tsenia ) 
unarmed (subgenus Txniarhynchus ) . 
unknown; see also 1 T. confusa (p. 
4. Rostellum: 
short, armed with 24 to 32 hooks; see also 2 T. solium (p. 
rather powerful, armed with 34 to 43 hooks; see also 2 T. pisiformis (p. 
very prominent, clrmed with 26 io 52 hooks; see <dso 2 T. temwformis (p. 
5. A circular ring surrounds head hack of suckers, which are directed postero- 
anteriorly; Asiatic Russia T. liominis (p. 
No such circular ring present 
6. Head, rather cuboid, 1.5 to 2 mm. in diameter; suckers 0.7 to 0.8 mm. in 
diameter T. saginata (p. 
Head rather small, 1.38 mm. broad, 1.03 mm. thick, 0.47 mm. long; suckers 
0.63 mm. in diameter; Africa T. africana (p. 
7. Segments: 
become longer than broad ( T. solium, T. pisiformis, T. crassicollis, T. 
saginata, T. confusa) 
become longer than broad only in last 100 proglottids T. saginata (p. 
become longer than broad in last half of worm T. solium (p. 
are longer than broad in nearly entire worm T. confusa (p. 
always broader than long; Africa; see 1 T. africana (p. 
unknown; Asiatic Russia; see 1 T. liominis (p. 
2 
3 
7 
8 
12 
15 
37) 
1 
32) 
36) 
41) 
43) 
4 
5 
44) 
37) 
41) 
43) 
36) 
6 
27) 
32) 
1 
27) 
37) 
44) 
32) 
36) 
a T. pisiformis and T. teniseformis are included in this table, although there are 
doubts regarding their occurrence in man. 
