Sometimes the existence of the tapeworm in man is restricted to the alimentary tract and the symptoms vary from trivial to severe, but sometimes (_Tenia solium_) the larval stage of the tapeworm invades the tissues and becomes encysted in various organs (brain, eye, etc.), where, as in the case of cerebral infection, it may result fatally. The encysted larva of _Tenia solium_ was at one time regarded as an independent animal species and named _Cysticercus cellulosae_. The condition known as "measly pork" is produced by the occurrence of this encysted parasite. So-called hydatid disease is due to the cystic growth produced by the larva of a species of tapeworm (_Echinococcus_) inhabiting the intestine of the dog. Human infection may be caused by contaminated food as well as more directly by hands soiled with petting infected dogs. Several varieties of tapeworms infesting fish, especially certain fresh-water species, may be introduced into the human body in raw or partly cooked fish. Methods for the prevention of tapeworm infection include the destruction of the larvae by heat--that is, the thorough cooking of all meat and fish--and the minimization of close contact with those animals, such as the dog and cat, that are likely to harbor parasites. Cleanliness in the preparation and serving of food, and attention to hand-washing before meals, and especially after touching pet animals, are necessary corollaries. UNCINARIASIS Hookworm infection (uncinariasis, ankylostomiasis) is commonly caused by infection through the skin of the feet, but the possibility of mouth infection cannot be disregarded, and in regions where hookworm disease exists methods of guarding against food contamination should be practiced, as well as other precautions. Billings and Hickey[93] believe that hookworm disease is contracted by unconscious coprophagy (from raw vegetables) much more frequently than is generally supposed. OTHER PARASITES A number of other parasitic worms (e.g., _Strongyloides_, _Ascaris_ or eelworm, and _Oxyuria_ or pinworm) may conceivably enter the human body in contaminated food, and while, as in hookworm disease, other modes of infection are probably more important, the liability to occasional infection by uncooked food must not be overlooked. [Illustration: FIG. 9.--_Lamblia intestinalis._ (After Neumann and Mayer.)] Various forms of dysentery or diarrhea have been attributed to infection with _Giardia (Lamblia) intestinalis_. Observations made by Fantham and Porter[94] upon cases contracted in Gallipoli and Flanders have given support to this view. Strains of this parasite of human origin have been shown to be pathogenic for mice and kittens. It is considered possible that these animals may act as reservoirs of infection and spread the disease by contamination of human food. FOOTNOTES: [90] The consumption of raw sausage made with pig meat is particularly likely to give rise to trichiniasis. [91] _Jour. Med. Research_, VI (1901), 64.