GENER/VL TECHXIC 25 



Wash in water. 



Transfer to 50-per-cent. alcohol. (May be omitted.) 



Transfer to 80-per-cent. alcohol. 



Transfer to 90-per-cent. alcohol. 



Transfer to absolute alcohol. 



Transfer to xylol. 



Transfer to fresh xylol. 



Mount in xylol-balsam. 



If an alcohol stain is used instead of an aqueous one, the carrying 

 down and up through the graded alcohols is omitted. 



If it is desired to stain double with eosin-haematoxylin (page 20) 

 use the above technic in staining with ha^matoxylin ; then the alcohohc 

 eosin stain before final transfer to absolute alcohol. 



IX. Injection 



For the study of the distribution of the blood-vessels in tissues 

 and organs, it is often necessary to make use of sections in which 

 the blood-vessels have been injected with some transparent coloring 

 matter. The injecting fluid most commonly used is a solution 

 colored gelatin. 



The gelatin solution is prepared by soaking i part gelatin in from 

 5 to 10 parts water — the proportion depending upon the consistence 

 desired — and when soft, melting on a water-bath. 



Various dyes are used for coloring the gelatin, the most common 

 being Prussian blue and carmine. 



Prussian blue gelatin is prepared by adding saturated aque- 

 ous solution Prussian blue to the gelatin solution, the proportions 

 depending upon the depth of color desired. Both solutions should be 

 at a temperature of 60° C. After thoroughly mixing, the blue gelatin 

 is filtered through cloth. 



Carmine gelatin is prepared by first dissolving i gm. carmine 

 in 30 c.c. distilled water. To this is added ammonia until the mixture 

 becomes a dark cherry red. A lo-per-cent. aqueous solution of acetic 

 acid is next added, drop by drop, with constant stirring until the mix- 

 ture becomes neutral. The carmine and gelatin solutions both being 

 at about 60° C, are now mixed in the desired proportions. If the 

 carmine injection mass is alkahne, it diffuses through the walls of the 

 vessels; if acid, there is a precipitation of the carmine which may 

 interfere with its free passage through the capillaries. If, however, 

 the alkaline carmine and gelatin be first mixed, and the lo-per-cent. 



