8 



INTRODUCTION. 



mounted in glycerin, glycerin jdly, or FarranC* solution, require 

 ringing to preserve them, a process much simplified by taking care 

 that at the time of mounting, only sufficient fluid is used to fill the 

 space between the glasses. The edge of the cover and the neighbouring 

 surface of the slide must be clean, so that the cement may hold. 

 Overflow of the mounting medium is first removed with blotting 

 paper moistened with water and then with alcohol. The slide is 

 centered on a turn table, which can be borrowed in the laboratory, 

 and a ring of thickened gold size applied with a small brush whilst 

 the table revolves at a moderate speed. Make the ring as narrow 

 as is consistent witli complete sealing and due hold upon the glass. 

 A second application of the same, or of Zinc white cement, will 

 complete the ringing. 



DRAWING AND MEASURING AN OBJECT. 

 Draw every object which you examine arid append marginal 

 notes connecting the latter with the parts noted by directing lines. 



Sketches are to enable you to stud}' later on the preparations which 

 you have made in class. It does not matter how slight the sketch is, 

 provided the principal features and their position in the preparation are 

 properly noted. Draw on paper faintly ruled 

 in squares, 1 avoid a cramped style and mere 

 mechanical repetition of detail. When the 

 subject is the section of an organ, draw the 

 general outline as seen under the low power. 

 Naked eye examination is of great help when 

 the section exceeds the dimensions of the iield. 

 Then givo high power views of those portions 

 which the preparation is meant to illustrate. 

 FIG. 2. Zeiss Eye-piece Light washes of water colour are effective 

 Cross-line Micrometer. additions, especially if they reproduce the 

 colours of the stains with which the tissues are treated. 



An eye-piece micrometer' 2 is a great help as it serves both as 

 a guide in drawing and as a scale for measurement. 



Measurement of an object. The simplest way is to standardise 

 the eye-piece cross-line micrometer for each combination of eye-piece and 

 objective, and to measure with it. A stage micrometer is necessary, and 



1 Suitable drawing books can be obtained from the Laboratory attendant, \V. 

 Bacon. 



* Eyepiece cross-line micrometer of Zeiss, divided 5 mm into 1 mm, price 5s. This is 

 dropped into the eye-piece, and rests upon the diaphragm, which must be adjusted by 

 pushing it up or down until the lines of the micrometer are in the focus of the eye-glass. 



