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 pseudo'podia-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. Eepeat the above observations on the white blood- 

 corpuscles of the frog or newt. 



