Laboratory Directions in General Biology (Classic Reprint)

The purpose of all laboratory work is to study nature at first hand. I ts educational value lies chiefly in the cultivation of accuracy and independence both of observation and of judgment. Each student is expected to make for himself the observations and experiments hereafter indicated. A record of every observation or experiment must be entered in the prescribed note book, under numbers corresponding to those in these Directions. This record should consist of drawings and descriptive notes, and every page should bear the name of its author and the date. The record for each topic must be inspected and passed by an instructor before any new topic may be undertaken. To each student in the laboratory is assigned a locker containing a microscope, reagents, glassware, etc., for the safe keeping of which he is held responsible. The microscope is the most complex and delicate instrument in this outfit and work with it should be preceded by a study of the following description of its parts and directions as to its use. I. THE MICROSCOPE. A. DESCRIPTION. The body or tube bears the lenses and is supported upon a stand which also carries a mirror to cast light upon the object examined through a hole in the flat stage upon which the object is placed. This hole can be made of various diameters by means of diaphragms. A lens for concentrating light, and known as a condenser may be placed between the mirror and the stage. The lens at the upper end of the tube is the ocular or eye-piece; there are two oculars, of different magnifying power. The combination of lenses at the lower end of the tube is the ob fee tire; in this microscope there are two objectives of different magnifying power, one marked 3, the other 6; the former (low power objective) is in focus, i. e., gives a clear image of the object examined when its lower end is about 2$ in. above the object, the latter (
(Typographical errors above are due to OCR software and don't occur in the book.)