That tea and coffee furnish us each day with a certain amount of wholesome liquid in which all organic life has been destroyed, remains a fact; they may be, in addition, when _properly made_ and of _proper strength_, of great value on account of their warmth, good flavor, and invigorating properties. There is no doubt that it is of the greatest importance that tea and coffee be used of _proper strength_; for if taken too strong, disorders of the system may be produced, necessitating their discontinuance, and thus depriving the individual of a certain amount of warm and wholesome liquid. =To Summarize.= The effects produced in water by boiling which have been spoken of are: (1) the expulsion of the atmospheric gases; (2) the precipitation of lime when in solution; and (3) the destruction of micro-organisms. The most important points to remember in connection with water are, that a certain amount each day is an absolute necessity of life, and that unless the supply be above suspicion it should be filtered and then sterilized. =Filtration and Sterilization of Water.= Filtration as a general thing is done by public authorities, but sterilization is not, and should be done when necessary by the nurse. For immediate use, simply boiling is said on good authority to be sufficient to destroy all _organisms_ then in the water. _Spores_ of organisms are, however, not killed by boiling, as they are very resistant to heat. Fortunately they are not common. As they do not develop into bacteria for some hours after the water has been boiled, they may be entirely gotten rid of by allowing them to develop and then destroying by a second boiling; but for all practical purposes, and under ordinary circumstances, water is rendered safe for use by boiling it once.[9] Should the water be very bad, boil it in a jar plugged with cotton for half an hour three days in succession, keeping it meanwhile in a temperature of 70° or 80° Fahr., so that any _spores_ of organisms which may be in it will have an opportunity to get into such a state of existence that they will be capable of being killed by the next boiling. The third treatment is for the purpose of making sure of any that may have escaped the first and second. PROTEIN The second of the food principles, protein, is a complex and very important constituent of our food. The protein compounds differ from all others as to chemical composition by the presence of nitrogen; they contain _carbon_, _oxygen_, _hydrogen_, and _nitrogen_, while the fats and carbohydrates are composed principally of _carbon_, _oxygen_, and _hydrogen_, but no nitrogen. The so-called extractives or flavoring properties of meats are nitrogenous, and are consequently classed with the protein compounds.[10]