216 PRACTICAL AN ATOM \. 



can then remove it from its parietal attachment, toward the mid-line of the body, 

 to the place where it is reflected on to the lungs, just as easily as a paper-hanger 

 removes his paper from the wall, for purposes of proper adjustment, before his 

 paste becomes set. (3) You now see the subpleural connective tissue the 

 medium intervening between the chest walls and the pleura. 



The structures now seen are (Figs. 150 and 152): The fibres of the inter- 

 nal intercostal muscles, terminating near the angle of the ribs posteriorly. The 

 space between this pleura and the vertebral column is occupied by fatty connec- 

 tive tissue, which must be dissolved in gasolene, ether, or benzine. Now you 

 will see, as in figure 150, the intercostal arteries, veins, and nerves lying on the 

 external intercostal muscles. You soon lose sight of these structures, for they 

 pass between the intercostal muscles. 



The thoracic gangliated cord of the sympathetic nerve (Fig. 152) is easily 

 dissected, but requires a delicate touch to preserve its integrity, such is the deli- 

 cacy of its structure. You can find a ganglion opposite the head of each rib. 

 Trace two little branches from this ganglion to the spinal nerve ; these branches 

 are the rami communicantes. 



Figure 151 shows the spinal nerves near their exit from the intervertebral 

 foramina, giving communicating branches rami communicantes to the ganglia 

 of the thoracic sympathetic cord. It also shows the manner in which the si.v 

 upper distribute their branches to the thorax, and the six Icnver their branches to 

 the abdomen by the splanchnic nerves. 



Branches of the Thoracic Gangliated Cord (Fig. 152). (i) To the spinal 

 nerves rami communicantes ; (2) branches connecting the ganglia ; (3) branches 

 of distribution. Notice the six upper ganglia give off branches to the aorta and 

 its branches in the thorax, to the bodies of the vertebrae and their ligaments, and 

 to the pulmonary and cardiac plexuses. Notice the six lower give off branches, 

 (i) to the aorta and its thoracic branches, (2) and unite to form the splanchnic. 



The splanchnics are the great abdominal visceral branches from the thor- 

 acic part of the gangliated cord ; they are named 



1. The greater splanchnic nerve (sixth, seventh, eighth, and ninth). 



2. The lesser splanchnic nerve (tenth and eleventh). 



3. The smallest or renal splanchnic nerve (twelfth). 

 Can these nerves be seen f 



Yes, easily. The scheme, as set forth in figure 152, can.be verified by any 

 student on any cadaver, with the proper care. Note that the three splanchnic 

 nerves pass through the diaphragm. When we study the thoracic aorta we will 

 see what becomes of the branches of distribution from the upper six thoracic 

 ganglia ; we must ask, Why are they so small, when the six lower are so large? 



The vena azygos major lies on the vertebral column. (Fig. 150.) It i 

 composed of the intercostal veins from the thoracic walls. The blood from th 

 intercostal spaces of the left side is collected by the vena azygos minor. Some 

 times two small azygos veins will be found on the lett side. The minor is tribu- 

 tary to the major azygos vein. Remember, the lett superior intercostal vein i> 

 tributary to the left brachio-cephalic ; the right to the vertebral vein. 



'The thoracic duct lies in a bed of fatty connective tissue, between the aorta 

 and the vena a/ygos major, on the vertebral column. It is confluent to the left 

 brachio-cephalic vein. It originates in the receptaculum chyli, on the second 

 lumbar vertebra. It passes through the aortic opening in the diaphragm. This 

 is easily inflated, in the recently-dead, before the material lias been embalmed. 

 To do this inflation, cut into the brachio-cephalic and find the orifice of the duct. 



The oesophagus extends from the pharynx to the stomach. It leaves the 

 thorax |>y the o-sophagcal opening in the diaphragm. Find it passing behind 

 (i) the arch of tin- aorta, (2) the trachea, (3) the left bronchus. (4) the left com 



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