‘Appendice (to Cobbold’s) Parasiti Interni degli Animali Domestice,’ p. 161, Firenze, 1874.--_Van Beneden, P. J._, “Iconographie des Helminthes ou des vers parasites de l’homme” (Vers Cestoïdes, pl. ii), Louvain, 1860.--_Welch, F. H._, “Observations on the Anatomy of _Tænia mediocanellata_,” ‘Quart. Journ. of Microsc. Science,’ vol. xv, 1875.--_Zenker_, in ‘S. B. Soc.,’ Erlang. iv, s. 71.--_Zurn_, ‘Zoopathologische und physiol. Untersuchungen,’ 1872. _Tænia solium_, Linneus.--This cestode was formerly known as the common tapeworm, but in England it is of far less frequent occurrence than the beef tapeworm. In contradistinction it is best to speak of it as the pork tapeworm. Though only one specimen is usually present, the bearer may entertain several worms of this species at one and the same time. The parasite has been known to science from the earliest times, though possibly not earlier than the measles, or Cysticerci, from which it originates. Hippocrates, Pliny, and Aristotle describe the full-grown worm; and, in regard to the larvæ, some have gone so far as to express their belief that the prohibition of swine’s flesh as food amongst the Jews and other Oriental people, was dictated by sanitary considerations. Weinland has suggested that the Mosaic commandment not to eat pork may have originated in an old popular notion “of the fact that tapeworm sometimes comes from this food.” Weinland’s hypothesis is probably correct, for if one supposes Moses to have been supernaturally informed that pork would produce tapeworm disease, one naturally asks why veal and beef should not also have been prohibited, seeing that these meats also frequently harbour tapeworm larvæ. A perfect pork tapeworm presents itself to the eye of the observer as a long, soft, white, jointed strobile, which, when alive, elongates and contracts itself with facility. Though commonly spoken of as a single creature, it is a compound of many individuals. These are variously called “cucurbitini,” “zooids,” “proglottides,” “segments,” “links,” or “joints.” When fully grown the segments are capable of detaching themselves and of enjoying a free and independent existence. Very annoying it is to the human bearer to be continually reminded of his unwelcome “guests” as they seek to quit his interior. The head of _Tænia solium_ is seldom seen in anatomical museums, although the evacuation of pork tapeworms is not of rare occurrence. Placed under the microscope, the head displays a quantity of dark, almost black, pigment granules, which are abundant at the base of the rostellum and in the neighbourhood of the hook-fangs. They are equally present and abundant in the pork measle proper, and in measles derived from the human subject. The cephalic hooks of this cestode are comparatively large, those of the greater circle individually measuring 1/156″, whilst the smaller hooks have a length of about 1/220″.