260 LABOR A TOR Y G UIDE IN PHYSIOL OGY. 



ing the ear as shown in Fig. 46. Quickly place the 

 cover glass, blood-side down on a clean slide and exam- 

 ine. 



4.. Precautions. Cover glasses must be clean, dry and free 

 from dust. The blood must be collected quickly or it 

 will form rouleaux. A warm stage prolongs the normal 

 appearance of the blood. Placing the microscope in 

 the incubator at body temperature for half an hour before 

 using will keep the slide warm for some time. In adjust- 

 ing the needle for puncture the condition of the patient 

 should be considered. A full blooded patient will require 

 a smaller puncture than an anaemic one. 



5. Observations. Note that the red corpuscles are round 

 in shape. As the plasma dries, it causes currents; as 

 the corpuscles float in these they strike each other, dent, 

 elongate and act like bags of jelly, returning to their 

 round shape when free. 



a. Red corpuscles. 



(1) Note biconcavity; what causes it ? 



(2) Are there variations in the size of the red cells? 



(3) What is crenation? Note when it begins. 



(4) Do you see two motions of red corpuscles ? De- 

 scribe any motion seen. 



(5) Do you see small motile bodies in the plasma? 



b. White corpuscles. 



(6) How do white corpuscles differ from red ? 



(7) Do they float as easily in the blood current? 



(8) How do they compare in size with red corpuscles ? 



(9) Why are white corpuscles smaller in fresh blood 

 than in dried specimens ? 



(10) What movements do you see? 



(11) Do you see any variation in size? 



(12) In which kind do you see the amoeboid move- 

 ments? 



