_To disinfect excreta or putrefying solutions_, enough disinfectant should be added to produce _in the solution or matter being disinfected_ the percentage of disinfectant necessary to act as such. Adding a small quantity of antiseptic to a large volume of fluid or solid is as useless as pouring a small quantity of antiseptic down a sewer with the idea that such treatment will disinfect the sewage. The mixture of the disinfectant with the matter to be disinfected must contain the standard percentage for disinfection. Chloride of lime is a common substance for use in this way. Potassium permanganate (1-100) and carbolic (1-100), and many manufactured bodies containing them, are also widely used. Drs. Hill and Abram recommend[108] that the excreta and disinfectant be thoroughly mixed and stand for at least half an hour. For various reasons they particularly advise _chinosol_ as the most convenient disinfectant for this specific purpose. _Antiseptics for wounds._ Carbolic acid (1-40) or corrosive sublimate (1-1,000) are commonly used in surgical practice. Boracic acid is one of the most unirritating antiseptics which are known. It may be used in saturated watery solution (1-30) or dusted on copiously as fine powder. It is especially applicable in open wounds, and as an eye-wash. _To disinfect hands and arms._ Operating surgeons are those to whom it is a most urgent necessity to cleanse hands and arms antiseptically. Carbolic acid (1-20, or 1-40) is used for this purpose. It is hardly necessary to add that in a case of infectious disease occurring in a household many of these modes of application, perhaps all of them, must be adopted. Formalin is probably the best gaseous disinfectant which we have, but its use does not, and should not, preclude the simultaneous adoption of other methods. APPENDIX It is proposed to add one or two notes on certain technical points in bacteriological work, with a view to assisting those medical men not able to obtain the advantages of a well-equipped laboratory, and yet desirous of occasionally attempting some practical bacteriology. 1. _General Examination._ All fluids may be examined for bacteria in two chief ways: (_a_) A small quantity may be placed on a cover-glass or slide, dried over a lamp or bunsen flame, and stained with aniline dyes for a few minutes. It is then ready for microscopic examination. It is obvious that the result will generally be a _mixture_ of bacteria, for which differentiating stains may be used (Gram, Ziehl-Neelsen, etc.). (_b_) A minute drop of the suspected fluid may be added to various fluid media (broth, liquefied gelatine, etc.) and then plated out upon small sterilised sheets of glass. In the course of two or three days the contained bacteria will reveal themselves in characteristic colonies, which may be examined, and if possible sub-cultured, and carefully studied.