It is, of course, assumed that the necessary amount of apparatus, chemicals, and other supplies is available, and that the laboratory desks, proper ventilation of the rooms, and safeguards in the case of all experiments fraught with danger have received the necessary painstaking attention on the part of the instructor, who must never for a moment relax in looking after these matters, which it is not the purpose to discuss here. At all times the student should work intelligently and be fully aware of any dangers that are inherent in what he is doing. It need hardly be said that a beginner should not be set at experiments that are specially dangerous. Having been given proper directions, the student should be taught to go ahead with confidence, for working in constant trepidation that an accident may occur often creates a nervous state that brings about the accident. Too much emphasis cannot be laid upon proper, definite laboratory instructions, especially as to kinds and amounts of materials to be used. Such directions as "take a _little_ phosphorus," for example, should be strictly avoided, for the direction as to amount is absolutely indefinite and may in the case where phosphorus or any other dangerous substance is used lead to dire accidents. The student should be given proper and very definite directions, and then he should be taught to follow these absolutely and not use more of the materials than is specified, as the beginner is so apt to do, thus often wasting his time and the reagents as well. Economy and the correct use of all laboratory supplies should be inculcated indirectly all the time. A fixed set of printed rules for the laboratory is generally neither necessary nor desirable when students are properly directed to work intelligently as they go, and good directions are given in the laboratory manual. Thus a spirit of doing intelligently what is right and proper, guarding against accidents, economizing in time and materials of all kinds will soon become dominant in the laboratory and will greatly add to the efficiency of the workers. Minor accidents are almost bound to occur at times in spite of all precautions, and the instructor should be ready to cope with these promptly by means of a properly supplied first-aid kit.