144 ELEMENTARY PHYSIOLOGY. [XIII. 



7. Carefully cut away the connective tissue around 

 the great vessels, tie the superior venae cavse 

 close to the heart, pass a silk ligature under- 

 neath the bulbus arteriosus and two underneath 

 the inferior vena cava. Make a loose knot in 

 them so that they can be tightened at any 

 moment. Cut across the aorta and sop up the 

 blood. With a fine pair of forceps raise up the 

 wall of the inferior vena cava close to the liver. 

 With fine pointed scissors, make a cut in the 

 vein and with the lower of the two ligatures tie 

 in it a small cannula, wash out the heart with 

 salt solution in the manner given in Lesson XII. 

 cp. 4. Inject a '5 p. c. solution of gold chloride 

 until the solution begins to issue from the aorta. 

 Then ligature the bulbus arteriosus. Again in- 

 ject, and whilst the heart is distended tie the 

 remaining ligature round the inferior cava just 

 beyond the end of the cannula. Cut out the 

 heart, immerse it in *5 p. c. gold chloride solution 

 and leave it for ten to fifteen minutes. Then 

 remove it to water, cut open the auricles and 

 shake so that the gold chloride is thoroughly 

 washed out of it. Transfer to water acidulated 

 with acetic acid and expose to light for a day ; 

 when it is well stained, observe the septum be- 

 tween the auricles, cut away the auricles from 

 the septum and cut away the ventricle, in re- 

 moving the last portions of the auricles it is well 

 to examine the septum from time to time under 

 a low power. Mount the septum in glycerine. 

 Observe 



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