This worm has a strong resemblance to the taenia solium, and in Britain it is probably more common than the latter, this being connected with the beef-eating character of our countrymen.

The strobilus is a larger worm than the taenia solium, measuring from about thirteen feet in the contracted state to about twenty-four feet when extended. Fig. 182 shows the head and neck of this worm. The head has no rostellum or circle of hooks, but it possesses four large sucking discs which are usually surrounded by zones of pigment. In the greater part of the worm the segments are broader than they are long, attaining a breadth of about half an inch. But as we come to the fully mature proglottides with embryoes in the uterus, then they are considerably elongated and at the same time narrower. The number of segments is greater here than in the taenia solium, reaching as high a figure as 1300. There are generally about eight discharged from the posterior extremity daily, and these very often find their way outwards, through the anus, by their own movement. The worm may live for many years, at least as long as eleven, and, as some assert, up to twenty or even thirty years.

The sexual organs, except the uterus, are essentially the same as in the taenia solium. The uterus,- however, presents in the mature proglottis a much larger number of lateral offsets, as many as twenty to thirty, and these mostly branch dichotomously instead of ramifying.

This tape-worm is liable to certain malformations, such as supernumerary joints inserted irregularly between the normal ones. The most peculiar malformation is the prismatic variety of the worm, shown in cross section in Fig. 184. In this form the worm is not a fiat band but a more substantial body, with three projecting borders.

Fig. 182. - Head of taenia saginata. x 16.

The structure is similar to that of the ordinary form, and the sexual pore is at the extremity of one of the projections. (See case by author in Glas. Med. Jour., xxxv., 1891).

Fig. 183. - Transverse section of proglottis of taenia saginata. At the upper end is the genital pore. Beneath it is the water-vascular canal. In the middle the central stem of the uterus is shown, x S.

Fig. 184. - Prismatic malformation of taenia saginata in transverse section. There are three equal limbs. The uterus has a common stem in the middle. The water-vascular canals are seen in section near the end of each limb, x 8.

The scolex form of this worm is found chiefly in cattle, and is hence sometimes called the Cysticercus bovis. It inhabits mostly the muscles, but is also met with in other organs. The cysticercus measures about the third of an inch, and is of a roundish shape. It is not known to occur in man.