The Microscope. 



179 



of many other salts, they shrink up and become crenated. This 

 action is supposed to be due to the abstraction from the corpuscle 

 of carbonic acid, for when this is restored to them, they resume their 

 former shape. Alkalis dissolve them rapidly, leaving scarcely a 

 trace behind. Tannic acid in a weak solution — about 3^ — has the 

 curious effect of concentrating the coloring matter into one corner 

 of the cell. The studeat should apply various reagents and study 

 the effects on the corpuscles. 



Compare the red blood- 

 cells of fishes, birds and reptiles 

 with those of the mammalia. 

 They will be found as a rule 

 to be very much larger, ellipti- 

 cal, and possessing large nuc- 

 lei. The nucleus causes a 

 bulging of the cell making it 

 biconvex at the middle. The 

 cells do not adhere and are not 

 so sensitive to reagents as the 

 mammalian corpuscles. 



White blood copuscles. 

 Because of the color they are generally spoken of as leucocytes. As 

 seen oq the slide they are spherical, granular, pearlish-white bodies, 

 somewhat larger than the mammalian red corpuscle aadmich smaller 

 than the reptilian, having a diameter in all vertebrates of about g^-Vo of. 

 an inch. They contain one or more nuclei which can be seen with- 

 out the use of a reageut as a round clear-cut body. A drop of 

 dilute acetic acid will serve to make them more prominent. In the 

 circulation they do not have a spherical shape, as, possessing inde- 

 pendent movement, they are continually changing their form. 

 This movement is called amoeboid from its rese nblance to the form- 

 changes of the amoeba. The mathols for studying this movemdat 

 will be considered in another chapter. 



Effects of reagents on the leucocytes. Acids and water make 

 them more transparent, develop the nuclei and finally dissolve 

 them. Alkalis dissolve them quickly. 



Blood-plates. Within the last few years another element has 

 been found in the blood: they are small, colorless, ovoid bodies 

 having a diamahar of aboub j^jjoij- of inch, and in numbar as com- 

 pare.! with the red corpuscles, about 1 to 25. When removed from 

 the circulation they quickly disinbegrate, and appear to have to do 



