HISTOLOGICAL DEMONSTRATIONS. 65 



84. Blood Crystals (H.) a. Haemoglobin may be 



readily prepared as follows : Kill a rat or mouse by the 

 inhalation of ether. Place a drop of its blood upon a 

 slide, and add twice its volume of water. Mix the two 

 with the point of a needle, and allow slight evaporation. 

 Prismatic crystals, either isolated or in rosettes, will be 

 found. These may be preserved by allowing the blood 

 completely to dry before the application of the cover-glass, 

 and then applying a drop of dammar solution and covering. 

 b. Hamin crystals are most readily prepared in con- 

 siderable quantity as follows : Place some finely-powdered 

 dried blood in a test tube ; add about one-twentieth of 

 chloride of sodium, and about ten times its bulk of glacial 

 acetic acid. Heat, and keep it a temperature not higher 

 than 50 C. for three or four minutes (the solution should 

 not be boiled). Filter and evaporate slowly. 



MUCUS. 



85. (H.) Mucous corpuscles may be obtained by 

 gently scraping the interior of the trachea of an animal 

 recently killed, or by hawking up some mucus from the 

 back of the throat. They have usually a single globular 

 nucleus ; sometimes, however, there are two or three. 

 They exhibit amoeboid movement, especially if they be 

 warmed to 38 C. on the hot stage (Fig. 49). Mucous 

 corpuscles may also be obtained from the urine by allowing 

 it to stand in a conical glass for six or seven hours until 

 the corpuscles are deposited. If the greater part of the 

 supernatant fluid be poured off, they can then be readily 

 obtained with a pipette (Fig. 45). Those from the urine 

 exhibit no amoeboid movement, even if they be warmed ; 

 probably because of the paralysing influence of the water 

 or other urinary constituent. 



EPITHELIUM. 



86. Stratified Squamous Epithelium (H.) Move 

 the tip of the tongue roughly over the gums and interior of 



F 



