In this chapter, the author proposes to place before the people a short and very elementary account, addressed rather to those who are not specially acquainted with biology than to those who are devoted to the science, in which he shall give the people a description of a few of the methods which are used in biological investigation, particularly with reference to the measurement and illustration of vital phenomena. The study of the life of plants and animals is in a very large measure an affair of measurement. The measurement to which the author wish to draw attention is the measurement of the time occupied in what the people call in physiology a “reflex” process. Some snuff finds its way into the nose; an impression is received, a change is produced in one’s nervous centres, and in consequence of that central change, a certain number of muscles are thrown into the action recognised as sneezing.