_Cause._ Said to be due to continued congestion of the liver, arising possibly from too much heat-giving food. _Treatment._ If the disease is suspected, give one grain of calomel as a purgative and feed on more green food. KIDNEY DISEASES _With the exception of gout, kidney diseases cannot be detected by external symptoms_ Gout (see page 63) is the commonest disease of the kidneys. In addition, there are some disorders of the kidneys (e. g., enlargement) that may be noticed on post-mortem examination. Little is known about these diseases; there are no symptoms that can be recognized before death, and no treatment can be recommended. LEG WEAKNESS _Constitutional weakness, to which the heavier breeds are more subject than are the lighter ones_ _Symptoms._ Fowls walk in an unsteady manner, without showing any specific cause for lameness. Young birds are more likely to be affected in this manner, particularly those of the heavier breeds. _Cause._ Too rapid growth, the bird outgrowing the strength of its legs. _Treatment._ Reduce the quantity of fat-producing foods. Care in the selection of breeding stock is important. LICE _Invariably present in small numbers, and likely to become a serious pest, if not persistently controlled_ _Symptoms._ Unthrifty look of fowl and signs of irritation; desertion of nest by setting hens; and, of course, the detection of lice on the fowl: this may be done by quickly turning over the feathers on the body and looking for the lice. [Illustration: FIG. 13.—LOOKING FOR LICE] _Cause._ Introduction of an infested fowl; neglect to dust fowls regularly to keep down lice, and to clean out fowl houses and change the straw of nest boxes. At the season that lice are likely to be most prevalent the poultryman should take precautionary measures. [Illustration: FIG. 14.—THREE LICE THAT COMMONLY AFFECT FOWLS (From Salmon.) _a._ Lipeurus variabilis. _b_, Menopon pallidum. _c_, Goniodes dissimilis.] _Description of lice._ Lice are small insects ranging in size from 1∕25 to 1∕8 of an inch. They breed rapidly, laying their eggs on the feathers. They are not blood-sucking insects, but cause much irritation to the birds they infest. Several species are found on fowls. Fig. 14 shows three of the common species. _Treatment._ Dust fowls with fresh insect powder (pyrethrum). Smear sulphur ointment on head and under wings, especially in the case of chickens. Infested fowls may be dipped in 2% creolin. Dust setting hens with a lice powder before putting them on their nests. Infested straw should be burnt, and boxes, nests, fixtures, etc., should be thoroughly sprayed with 2% creolin. LIMBER-NECK _An occasional complaint_ _Symptoms._ The muscles of the fowl’s neck become so relaxed that they cannot support the head.