DIRECTIONS FOR LABORATORY WORK 



I. INTRODUCTORY EXERCISE 



This exercise is designed to acquaint the student with the diagnostic 

 features of certain more common laboratory materials which may become 

 incorporated with histologic preparations; and to serve as a preliminary 

 test of the student's facility in the use of the microscope and of his 

 acuity of observation. 



(1) Mount under cover glass in a drop of water a human hair, a 

 strand of wool, and a few rabbit hairs. Examine with the low power 

 (l.p.) of the microscope. Sketch (1) a short segment of each as seen 

 with the high power (h.p.). 



(Use only medium hard pencil. Make no mark that does not cor- 

 respond with some structural feature of specimen under observation.) 



In what features do the three hairs resemble each other? 



In what features do they differ? 



Compare surface features with structure of axis by changing the 

 level of focus. 



(2) Mount on separate slides in water: 



(a) a few cotton fibers 



(b) a strand of silk 



(c) some finely separated threads of linen. 



Examine with l.p. Note differential features. Sketch (2, 3, 4) short 

 segments under h.p. 



(Label all drawings. Print labels. Use broken line leaders, ending 

 with arrow at point or structure to be indicated.) 



(3) Make water mount of a small mass of a common mould. Notice 

 the long branching filaments (hyphae) ; and the spheroidal spores, from 

 which hyphae may occasionally be seen sprouting. Sketch (5) portion 

 of a hypha. Are the hyphae segmented? 



(No attempt should be made to execute a drawing of a preparation 

 until after a precise conception has been acquired of the structure under 

 examination as the result of an intelligent study with both the low and 

 high powers of the microscope.) 



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