III.] THE PROTEUS ANIMALCULE. 23 



B. WHITE BLOOD-CORPUSCLES, (human). 



Prick your finger and press out a drop of blood : spread 

 out on a slide under a coverslip, avoiding pressure, and 

 surround the margin of the coverglass with oil. Neglect 

 the pale yellow homogeneous (red) corpuscles, and examine 

 the much less numerous, granular, colourless, ones. 



Note their 



1. Size: (measure). 



2. Form : changing much like that of the Amoeba, but 

 less actively. Draw at intervals of ten seconds. 



3. Structure : Some more and some less granular ; but 

 no distinct ectosarc, endosarc, and vacuole as in the 

 Amoeba. Nucleus rarely visible in the fresh state. 

 No contractile vesicle. 



4. Treat with dilute acetic acid : the granules are cleared 

 up, and a nucleus is brought into view in a more or 

 less central position. If the acetic acid has been too 

 strong the nucleus will be constricted and otherwise 

 distorted. 



5. Stain with magenta, and iodine ; the whole becomes 

 coloured, the nucleus most intensely. 



6. Place on the hot stage, and gradually warm up to 50 C. 

 The movements are at first rendered more active,, but 

 ultimately cease, the pseudopodia-like processes being 

 all retracted and the whole forming a motionless 

 sphere. 



Let the specimen cool again ; the movements are not 

 resumed ; the protoplasm having passed into a state 

 of permanent coagulation or rigidity. 



7. Repeat the above observations on the white blood- 

 corpuscles of the frog or newt. 



