I.] DISSECTION OF A RABBIT AND 'OF A DOG. 21 



Observe the branches going from these ganglia 

 towards the heart. Observe also the depressor 

 nerve passing to the heart. 



From the first thoracic ganglion trace down the 

 thoracic sympathetic nerve trunk lying on the 

 heads of the ribs with the ganglia (twelve in all) 

 and the rami communicantes connecting each 

 ganglion with its corresponding spinal nerve. 



20. Trace out the splanchnic nerve on one side ; it 

 will be found to separate from the sympathetic 

 at the 8th, 9th, or 10th thoracic ganglion. At 

 first sight it appears to be the continuation of 

 the sympathetic instead of a branch of it ; since 

 the sympathetic at its lower part becomes more 

 transparent, and running in a groove between 

 two muscles, is rather easily overlooked. The 

 splanchnic receives branches from each of the 

 thoracic sympathetic ganglia below its origin. 



27. Tie a tube in the trachea and distend the lungs, 

 note the appearance of the distended lungs. 

 Cut out the heart 1 with the lungs attached, and 

 trace the pulmonary arteries and veins. 



28. Having reflected on either side the skin of the 

 neck of the dog, and cleared away the fascia of 

 connective tissue, observe the muscles under- 

 neath. 



a. The atemo-hyoid close to the median line. 

 It runs from the sternum to the hyoid bone. 



1 The heart may be dissected in the manner given for the sheep's 

 heart in Lesson xn. 



