After the patient recovers, the room should be disinfected with formaldehyde gas obtained from the substance known as "formalin." This gas may now be obtained from the formalin without the use of heat in the following manner: When everything is ready, and the room properly sealed, thirteen ounces of permanganate of potash to each quart of formalin are placed in a large vessel, the room being closed immediately after the two substances are put together; it is important that the permanganate be placed in the vessel first. When this method is employed a quart of formalin should be used to each one thousand cubic feet of air-space in the room. As the gas, by this process, comes off with great rapidity, it is not necessary to keep the room closed more than about four hours. This method is to be advised for the reasons that it acts more quickly than the older one, and there is never danger of fire. In cases where houses are too open to permit of disinfection by means of gas, the sick chamber should be thoroughly washed with a solution of corrosive sublimate, carbolic acid or some other good disinfectant. HOOK-WORM DISEASE. It has been only recently recognized that a large percentage of the invalidism and a great number of the deaths yearly in the southern portion of the United States are caused by a very small intestinal parasite known as the _Necator americanus_, or hook-worm. This parasite has unquestionably existed over the area just named since the advent of the Negro--recent investigations having shown that the worm is in all probability of African origin. This hook-worm disease is probably the most common of all the serious diseases prevalent in the South, and as it is easily curable, and can be readily prevented, there is no matter which should be of greater interest to the people in the infected regions, especially those who live in villages or on farms. _Character of the Disease._--The animal parasite called hook-worm closely resembles, externally, the pin-worm which so often occurs in children. The female, which is larger than the male, measures somewhat more than half an inch in length, and has the thickness of a knitting-needle; the male is between a quarter and three-eighths of an inch in length as a rule. The parasite possesses around its mouth a row of minute plates somewhat resembling hooklets, by means of which it grasps hold of the mucous membrane of the intestine and bruises it sufficiently to cause the blood to flow; with this blood the parasite nourishes itself. At the same time the worm injects into the tissues a poison which has much to do with the symptoms that occur in the disease that it produces.