86 Modern Microscopy. 



gelatine solution, stirring well all the time; then filter 

 through flannel. 



Watery Solution of Berlin Blue. Dissolve 2J drams of 

 the blue in 18 ounces of distilled water and filter. This 

 fluid is useful for injecting lymphatics. 



Injecting Apparatus Required. An injecting syringe 

 fitted with a stop-cock and several cannulae of various 

 sizes. 



Directions for Injecting 1 . The animal to be injected 

 should be killed by chloroform, so that the vessels may 

 be dilated, and injected while warm ; if possible it should 

 be placed in a bath of water at a temperature of 40 C. 

 Expose the artery of the parts to be injected, clear a 

 small portion of it from the surrounding tissues, and 

 place a ligature of thin twine or silk round it. With 

 sharp scissors make an oblique slit in the wall, of the 

 vessel, insert the cannula, and tie the ligature firmly over 

 the artery behind the point of the cannula, into which put 

 the stop-cock. Fill the syringe with injection fluid, which 

 must not be too warm, and take care not to- draw up any 

 air-bubbles ; now insert the nozzle of the syringe into the 

 stop-cock and force in a little fluid ; remove the syringe, 

 so that the air may escape, insert the syringe again, and 

 repeat the process until no air-bubbles come out of the 

 stop-cock. You may then proceed slowly with the injec- 

 tion. Half an hour is not too long to take over the injection 

 of an animal of the size of a cat. One judges of the com- 

 pleteness of an injection by looking at the vascular parts, 

 such as the tongue, eyelids, and lips. When the injection 

 is complete shut the stop-cock, remove the syringe and 

 cannula, and tie the ligature round the artery. Now place 

 the animal in cold water for an hour to set the injection- 

 fluid. When quite cold dissect out the organs, cut them up 

 into small pieces, and place them in methylated spirit to 

 harden, and change the spirit every twenty-four hours for 

 the first three days. The hardening will be complete in 

 ten days. 



