204 



THE AMERICAN MONTHLY 



[July, 



preparations are to be made in this way and placed, blood-side 

 up on the filter paper before you and allowed to dry. If the 

 blood is to be taken from a mammal, a small incision is made 

 in the ear. From the flowing blood a small drop is caught on a 

 cover as above described. 



Amphibian or reptilian blood is obtained from the heart. 

 The blood preparations may be fixed by placing them in a so- 

 lution, composed of equal parts of absolute alcohol and ether, 

 in which they remain for an hour as suggested by Nikiforoff or 

 as Dr. Ehrlich recommends, by exposing them to a temperature 

 of from 100° to 110° C for from one-half hour to one hour. 



In connection is used a very simple apparatus shown in above 

 cut for fixing the blood preparations. It consists of a copper 

 plate about 15 inches long, 4 inches wide and i inch thick, 

 resting on a metal support. The copper plate is heated at one 

 end with an alcohol or gas flame. If then, at the end of fifteen 

 minutes the glass rod which has been dipped into the water 

 be passed over the plate, beginning at the end away from the 

 flame, a place is reached where the water begins to boil. This 

 region of the copper plate represented by a dotted line on the 

 diagram is looked upon as having a temperature of 100° C. The 

 blood preparations are placed on the plate (blood side up) be- 

 tween the flame and this imaginery line, near the line, and 

 heated for a time differing with the stain used. 



If the Neutrophile stain is to be used, the cover glasses on 

 which the blood has been spread need to be fixed for fifteen to 

 thirty minutes. The preparations are then placed, blood side 



