[Illustration: 97. Echidnophaga gallinacea infesting head of chicken. After Enderlein.] Castellani and Chalmers recommend as prophylactic measures, keeping the house clean and keeping pigs, poultry, and cattle away therefrom. "High boots should be used, and especial care should be taken not to go to a ground floor bathroom with bare feet. The feet, especially the toes, and under the nails, should be carefully examined every morning to see if any black dots can be discovered, when the jigger should be at once removed, and in this way suppuration will be prevented. It is advisable, also, to sprinkle the floors with carbolic lotion, Jeyes' fluid, or with pyrethrum powder, or with a strong infusion of native tobacco, as recommended by Law and Castellani." _Echidnophaga gallinacea_ (fig. 96) is a widely distributed Hectopsyllid attacking poultry (fig. 97). It occurs in the Southern and Southwestern United States and has been occasionally reported as attacking man, especially children. It is less highly specialized than _Dermatophilus penetrans_, and does not ordinarily cause serious trouble in man. CHAPTER IV ACCIDENTAL OR FACULTATIVE PARASITES In addition to the many species of Arthropods which are normally parasitic on man and animals, there is a considerable number of those which may be classed as _accidental_ or _facultative_ parasites. Accidental or facultative parasites are species which are normally free-living, but which are able to exist as parasites when accidentally introduced into the body of man or other animal. A wide range of forms is included under this grouping. ACARINA A considerable number of mites have been reported as accidental or even normal, endoparasites of man, but the authentic cases are comparatively few. In considering such reports it is well to keep in mind von Siebold's warning that in view of the universal distribution of mites one should be on his guard. In vessels in which animal and other organic fluids and moist substances gradually dry out, mites are very abundantly found. If such vessels are used without very careful preliminary cleaning, for the reception of evacuations of the sick, or for the reception of parts removed from the body, such things may be readily contaminated by mites, which have no other relation whatever to them. Nevertheless, there is no doubt but that certain mites, normally free-living, have occurred as accidental parasites of man. Of these the most commonly met with is _Tyroglyphus siro_, the cheese-mite.