31 



tion ; apply a cover glass. Is any change observable ? If so, what ? 

 Is the fluid truly normal ? 



(d) Distilled water . Place upon a clean slide a drop of fresh 

 blood and place beside it a small drop of distilled water ; cover. 

 What is the effect of the water upon the corpuscles ? Where the 

 blood and water meet observe the ' changes ; find some corpuscles 

 entirely in the water. What is the meaning of the change ? 



(f) 2 % salt solution. Place a small drop of blood upon a slide, 

 cover, and at the side oi the cover glass place a drop of a 2% solu- 

 tion of common salt. What is the effect of the solution upon the 

 corpuscles with which it comes in contact ? Meaning ? 



(a?) 2% acetic add. Make another preparation of fresh blood 

 and at the side of the cover glass place a drop of a 2% solution of 

 acetic acid. Note the effect of the solution upon the red corpuscles 

 and compare with the action of distilled water. What is the effect 

 of the solution upon the white corpuscles ? What is the meaning 

 of these experiments in connection with the structure of the red 

 corpuscles ? 



42. Dry preparation. With a piece of lens paper wet with 

 95% alcohol wipe off the finger at the point where it is intended to 

 obtain blood ; prick the finger as in 40, and as directed in § 121, 

 ( I.) , prepare six or more blood films upon clean covers ; allow two 

 of them to dry and place the others in a watch glass of ether-alcohol 

 for 43. 



Allow the two films saved out to dry thoroughly, then warm 

 gently and mount the best (or both) film side down upon a shellac 

 ring prepared at some previous time (§ 103, a~). Select a place where 

 the film is thin and even to study the appearance of the dried cor- 

 puscles. Choose several corpuscles that are not distorted and with 

 the ocular micrometer for which you determined the valuation 

 measure their diameter in microns. Compare with the size given 

 in the text-book. 



4.3. Stained preparations. (§§ 121-123). Allow the prep- 

 arations that were placed in ether-alcohol to fix for one hour or 

 longer, remove them and allow them to dry for a few minutes, when 

 they may be stained immediately or later (at your second period). 

 Stain the blood films in two ways : (a) with eosin and hematoxylin 



