Dissections, 153 



DISSECTIONS. 



I. SHEEP'S HEART*. 



Preparatory. Inject with coloured size the Coronary 

 arteries from their orifices in the sinuses at the root of the 

 Aorta. 



The only difficulty in dissecting a Sheep's heart lies in 

 the mass of fat you have to contend with round its base 

 (i.e. that portion which is directly attached to the great blood 

 vessels). Now in order to remove the fat, do not attempt to 

 slice it away from the outer surface ; if you do, you will 

 assuredly cut through superficial vessels (i.e. the coronary 

 arteries and veins) and cut into others : but taking each 

 portion of fat separately, carefully separate it by dissection 

 from the subjacent tissue, and never cut across any structure 

 until you are perfectly satisfied as to what it is. 



EXA.MINATI0N OF THE ExTERiOR. When the fat has been 

 cleaned away ; taking the Heart in your hand you will note 

 one half to be more easily indented than the other ; this 

 marks the area of the thin- walled right f Ventricle : the thick- 

 walled left Ventricle occupying the larger part of the anterior 

 surface. 



* In order to eec the first course of the vessels after learing the heart, it will 

 be well to obtain the heart and lungs together : as, however, we purpose tracing 

 them when dissecting the complete specimen of a Mammal, we have described 

 here the heart alone. 



t In using the terms right and left we speak of the heart as situated in the body. 



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