I] 



MILK, FIBRES, VEGETABLE ORGANISMS. 



99 



Now use the fine adjustment, and bring the outlines of the object 

 in the field sharply into view. 



It is of the greatest importance that the student should be taught 

 to describe the objects which he sees, and also to make sketches of 

 them. To facilitate the description of isolated objects, the follow- 

 ing heads may be adopted : 



Shape. 

 Border. 

 Surfaces (upper and lower). 



Size. 

 e. Colour. 



/. Transparency and relation to light. 

 g. Contents. 

 li. Effects of reagents. 



In the object under examination there is a large number of. 

 minute bodies floating in a fluid. Describe the appearance of the 

 floating particles under the following heads : 



(a.) Shape. The milk globules (fig. 52) are spherical, as can be 

 shown by touching the edge of the cover-glass with a needle, and 

 then observing them as they 

 rotate in the field of the micro- 

 scope. Moreover, if one be 

 focussed, its outline comes 

 gradually into focus, and dis- 

 appears gradually, while optically 

 with regard to light these bodies 

 behave as globules, and not as 

 discs. 



(6.) Border. Smooth and 

 regular. 



(-".) Surftiws. Elevate the 

 objective by means of the fine 

 adjustment until the, upper sur- 

 face of the globules comes into 

 view ; depress it again slowly 

 and then examine the globule 



throughout its entire thickness, until its under surface is brought 

 into view. Both surfaces are smooth. 



(d.) tiize. The globules are not all of the same size. If desired, 

 measure their actual size (p. 20). 



(e.) Colour. The smaller ones appear colourless, but some of the 

 larger may havQ tb<i slightest tiuge/rf, a /amkyeJlow.,.. 



(/) Transparent^ qiidyilaticnl &> Ifyhfttfkey* Jre transparent, 

 because the outline of a subjacent one cah be eeli Ih'rough a globule 



FIG. 52. Milk Globules, x 400. 



