The ova are present in the stools of infected persons, often in great numbers. They are spheric or ovoid, yellow in color, and have a thick, radially striated shell ([Fig. 101]). Their greatest diameter is 30 to 40 µ (about four or five times the diameter of a red blood-corpuscle). Vegetable cells, which are generally present in the feces, are often mistaken for them.
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FIG. 96.—Head of Tænia saginata (Mosler and Peiper). |
FIG. 97.—Head of Tænia solium (Mosler and Peiper). |
(2) Tænia solium, the pork tape-worm is very rare in this country. It is usually much shorter than Tænia saginata. The scolex is surrounded by four sucking discs, and has a projection, or rostellum, with a double row of horny hooklets (Fig. 97). The uterus has only seven to ten branches ([Fig. 100]).
The ova closely resemble those of Tænia saginata, but are a little smaller ([Fig. 101]).
(3) Bothriocephalus latus, the fish tape-worm, is the largest parasite of man, sometimes reaching fifty feet in length, although generally not more than half so long. It is common in some countries of Europe and in Japan, but is very rare in this country. The head is not unlike the bowl of a spoon in shape. It is unprovided with either suckers or hooklets, but has two longitudinal grooves which serve the same purpose (Fig. 98). The uterus, which is situated in the center of the segment, is roset-shaped ([Fig. 100]).
| FIG. 98.—Head of Bothriocephalus latus: a, a, Bothridies; b, neck (Blanchard). |
The larval stage is found in fish, especially the pike.
| FIG. 99.—Egg of Bothriocephalus latus, showing lid and yolk granules (photograph by F. C. Wood). |
The ova are characteristic. They measure about 45 by 70 µ, are brown in color, and are filled with small spherules. The shell is thin, and has a small hinged lid at one end (Fig. 99).
Bothriocephalus latus is interesting clinically because it often causes a very severe grade of anemia.