MICROSCOPIC TECHNIQUE. 21 



pursued: Sever the costal cartilages on each side of the sternum; 

 lift up the sternum and bend it forward so as to expose the heart. 

 Make a slit into the right auricle to allow the escape of the blood. 

 Snip off the end of the heart and slit open the left ventricle- Insert 

 the canula of the injecting syringe into the aorta, carefully tying the 

 same upon the end of the canula. Now, having filled the syringe 

 with normal saline solution at body temperature and having filled 

 the canula with the same, using pipette, attach the two, and with 

 a gentle pressure force the liquid through the system until the ar- 

 teries and veins have been thoroughly relieved of blood. Eepeat the 

 same process, using Carter's Carmine Mass. By observing the lips 

 and other structures it can be determined when the circulatory sys- 

 tem is filled with the injecting fluid. ISTow, make a ligature around 

 the aorta, just beyond the canula, and the syringe can be removed. 

 In fifteen minutes the tissues can be cut up into small blocks (these 

 blocks should be in the form of cubes or rectangles from 1 cc. to 2 

 cc. in size), and placed in the fixing fluids. 



Epithelium. For purposes of study epithelium may be obtained 

 from the casts of a frog or newt, from the scrapings of the human 

 lip, from the throat of a frog, and the scrapings of the trachea of a 

 pig. This material may be readily obtained by macerating the ob- 

 ject in weak alcohol. Keep the specimens in eighty per cent al- 

 cohol, and use when required. 



Cartilage. Fix in absolute alcohol; harden with increasing 

 strengths of alcohol, and embed in paraffin. Stain with carmine. 



Mucous Tissue. Fix small pieces of the umbilical cord with ab- 

 solute alcohol, harden with alcohol, embed in celloidin, and stain 

 with hsematoxylin. 



Bones and Teeth. Fix in ninety-five per cent alcohol three days; 

 decalcify in a saturated aqueous solution of picric acid or in a ten 

 per cent solution of nitric acid. This process will require from five 

 to ten days. When the bone or tooth is thoroughly softened, trans- 

 fer to ninety-five per cent alcohol, changing in three days to fresh 

 alcohol. Embed in celloidin. Specimens embedded in paraffin 

 should not be overheated. 



Muscle. Fix in absolute alcohol; harden with increasing 

 strengths of alcohol ; embed in paraffin ; stain with lithium carmine. 



