METHOD OF PREPARING TISSUES AND ORGANS. 39 



sternum, expose the pericardium, open it, and with a pair of scissors 

 make a snip into the right auricle of the heart, and allow the animal 

 to bleed freely. 



It is best to begin by removing the brain and spinal cord. They 

 are hardened in Miiller's fluid or potassic bichromate (2 per cent.), 

 and must be placed in a large volume of fluid. A few spinal 

 ganglia should also be found and hardened in the same way. 



Remove the trachea and lungs, and fill the lungs and trachea of 

 the rabbit with a \ per cent, solution of chromic acid. 



This is readily effected by tying a funnel into the trachea and 

 pouring in the fluid. By squeezing the lungs gently much air is 

 forced out, and the fluid gradually runs into and distends the 

 lungs, which, when distended, are placed in a large volume of the 

 same fluid. The chromic acid and spirit mixture may be used 

 instead of pure chromic acid. 



Fill the windpipe and lungs of the guinea-pig with J per cent, 

 silver nitrate. (See Lungs.) 



Remove the heart, and harden it in alcohol, after washing away 

 any blood with normal saline. 



The central tendon of the diaphragm may be preserved for 

 silvering. (Lesson IV.) 



The omentum and mesentery, if desired, are silvered. (Lesson 

 IV.) 



( )ppn the abdomen, remove the liver, cut it into small pieces ; 

 harden some pieces in Miiller's fluid, and others in spirit. 



Take out the tongue and oesophagus ; harden them in Miiller's 

 fluid. 



Open the stomach and intestine, wash away any food residues 

 by means of normal saline. Harden part of the stomach cardiac 

 and pyloric in absolute alcohol, other pieces in Miiller's fluid, 

 and others in corrosive sublimate, and small pieces in osmic acid. 

 (See Lesson on Stomach and Intestine.) 



The duodenum and small and large intestine are hardened in 

 the same way, although the bichromate and chromic acid mixture 

 (p. 29) is particularly good for the small intestine. 



The salivary glands and pancreas are removed and hardened by 

 the methods given under these headings, i.e., small pieces are placed 

 in each of the following solutions : Absolute alcohol, osmic acid, 

 corrosive, sublimate, &c. 



Remove the lower jaw, cut it into short pieces, place it in .2 per 

 cent, chromic acid for a few days, and then decalcify it in chromic 

 and nitric fluid. This will yield sections of softened tooth. 



Remove the kidneys, cut one longitudinally and the other trans- 

 versely. Using the kidneys of different animals, harden pieces of 

 each in the following fluids : Miiller's fluid, chromic acid and spirit, 



