BY DR. KLEIN. 27 



drop of newt's blood being then added to it and covered. It 

 is seen that the colorless corpuscles have undergone no mate- 

 rial change, but that, in some instances, their movements are 

 not quite so active. The colored corpuscles, which in our 

 previous examination we have disregarded, are now seen as 

 smooth oval elliptical disks, which, when looked at edgewise, 

 present an outline as if they were oblong rods. Those which 

 lie horizontally look, for the most part, like greenish-3 r ellow 

 bodies of oval form; in some of which we can distinguish a 

 central elliptical nucleus. Soon, changes occur, in consequence 

 of which the color becomes unequally distributed, the margins 

 are more or less curved, or the surfaces marked with what look 

 like folds. These appearances are referable probably to a pro- 

 cess analogous to coagulation. 



Method of Retarding Evaporation. If it is intended 

 to keep a preparation of this kind long under observation, it 

 is necessary to add saline solution from time to time from a 

 pipette. If, however, as is often the case, it is of importance 

 to keep an individual corpuscle in the field, this method can- 

 not be emploj'ed without great risk of the object being carried 

 away by the stream. To avoid this result, it is a good plan 

 to place a drop or two of solution near each of two opposite 

 margins of the cover-glass. By these drops the liquid under 

 the glass is preserved from evaporation, because the space in 

 the immediate neighborhood of the margin is kept saturated 

 with moisture. 



We may now proceed to study the action of other reagents 

 on blood already treated with saline solution. We use the 

 so-called method of irrigation. On one side of the cover- 

 glass a small strip of blotting-paper is placed, while the re- 

 agent is discharged from the pipette at the opposite edge. 

 When the paper has become saturated with liquid it is replaced 

 by another, and the process repeated, so that a constant cur- 

 rent is maintained through the preparation. If the colored 

 corpuscles are the special subject of study, it is best to wait 

 until they have shrunk, for we are then sure that many of 

 them will have had time to sink and adhere to the surface of 

 the slide. If this precaution is neglected, they are apt to be 

 swept away by the current. 



Action of Distilled Water. In blood preparations irri- 

 gated with distilled water, the movements of the colorless 

 blood corpuscles gradnall}- cease. The inequalities, corre- 

 sponding to the processes, disappear, while the corpuscle en- 

 larges, and assumes the globular form. From one to four (or 

 even more) round vesicular nuclei come into view. Soon tin- 

 nuclei coalesce to form a single mass, also having a vesicular 

 character, which not un frequently exhibits a rotatory move- 

 ment within the corpuscle. The substance which surrounds 



