i 7 o 



Ehrlich recommends the fixing of the preparations by 

 heat. He suggests a very simple apparatus, shown in Fig. 

 II, by means of which the blood may be fixed. 



It consists of a copper plate about 15 inches long, 4 

 wide, and -J inch thick. The copper plate is heated at one 

 end by means of an alcohol or gas flame. If then, at the 



oo. 



Fig. II. Plate for heating blood preparations, 

 blood preparations; F, tripod. 



A, copper plate; C, 



end of 15 minutes a glass rod which has been dipped into 

 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 is looked upon as 

 having a temperature of 100 C.; it is represented by a 

 dotted line in the diagram. The blood preparations (C) 

 are placed on the plate (blood side up) between the flame 

 and this imaginary line (nearer the latter), and heated for 

 a time varying with the stain to be used. 



The blood of any vertebrate may be spread and fixed 

 as above directed. When desired to make preparations 

 from fish, amphibian, or reptilian blood, the blood is most 

 easily obtained from the heart. This, after exposure, is 

 nipped with a pair of scissors, a small drop of the flowing 

 blood is picked up on the end of a clean glass rod, quickly 

 transferred to cover glass, and spread in the usual way, 

 Bird's blood is readily obtained from one of the toes, which, 

 after anaesthetizing the animal, may be cut or partially 

 amputated ; a small drop is taken from the flowing blood, 

 and spread. Preparations of red bone marrow, of the spleen, 

 or of lymph glands may also be prepared after this method. 

 Very small pieces of the tissue are placed between two 



