LABORATORY MANUAL OF PHYSIOLOGY. 



2. Instead of the blood slide, place the stage micrometer under 

 the microscope. With the help of this, find the exact value of the 

 spaces between the lines of the ocular micrometer. Remove the 

 stage micrometer and again place the blood specimen under the 

 microscope. With the ocular micrometer, measure the dimensions 

 of twenty-five red corpuscles. Compare the size of the white 

 corpuscles with that of the reds. 



3. Pith a frog. From the wound thus made, secure some blood 

 for microscopical examination. How do the red blood cells of the 

 *rog compare in size, form, and nucleation with the red cells of man 

 and of the rabbit or dog ? In frog's blood what is the relative size 

 of red and white cell ? 



IV. STAINING OF THE BLOOD CELLS AND DIFFERENTIAL COUNT 

 OF THE LEUCOCYTES. 



A dried blood smear or film is usually employed for this pur- 

 pose. The blood smear may be made in one of two ways, either 

 on a slide or upon a cover slip. If the former method is employed, 

 the smear is allowed to dry on the slide, is stained, and examined, 

 without the use of a cover glass. If the latter method is used, the 

 smear is dried, fixed, and stained upon the cover slip and this is 

 then inverted, smear side down, upon a slide over a drop of balsam 

 or a shallow air cell. 



1. The Smear on the Slide Direct. Take two slides. Touch 

 the edge of one to the drop of blood. With this slide forming an 

 angle of about 25 with the other, quickly and firmly apply its 

 blood-stained edge to the other slide and sweep it over the surface. 



2. The Cover-Glass Smear. For this purpose, two cover 

 slips are used. One of the cover slips is carefully applied to the 

 drop of blood, so that a drop adheres to the centre of the slip. This 

 slip is then applied to the other and the blood allowed to spread in 

 a thin film between the two. After this has occurred, the two slips 

 are carefully drawn apart and the smears allowed to dry in the air. 



3. Staining the Films. The simplest and best available 

 blood-staining reagent at the present time is that devised by 



