346 



DISCOVERY REPORTS 



It may be observed also that there is an 

 increasingly generous blood supply to the 

 intercostal muscles proceeding forwards. 

 The branches from the posterior thoracic 

 are bi-seriate (Fig. 6), and tend to be of 

 larger calibre rostrally than posteriorly. The 

 posterior thoracic arteries and veins corre- 

 spond to a much enlarged and accentuated 

 superior intercostal system, such as is found 

 in other mammals. By their contact with 

 the rete mirabile the first two intercostal 

 spaces are probably the most generously 

 supplied with blood of the whole series. 



RELATION TO NERVES 



The pneumo-gastric nerve (Fig. 3 d 2 and 

 Fig. 7/) accompanies the carotid artery 

 and the jugular vein, passing above the short 

 subclavian vein and under the subclavian 

 artery to its destination in the roots of the 

 lungs and heart. 



The phrenic (Fig. 3 d> and Fig. 7/) is de- 

 rived from the 4th cervical spinal nerve, and 

 accompanies the pneumo-gastric as far as the 

 great vessels, where it diverges and crosses 

 the body of the lung to the diaphragm. 



The 5th, 6th, 7th and 8th cervical spinal 

 and the 1st thoracic spinal nerves (Fig. 7 

 cr 5 - 8 , tr 1 ) contribute to the cervico-brachial 

 plexus, passing through a slit in the scalene 

 muscle to reach it. 



The cervical sympathetic chord (Fig. yg) 

 accompanies the pneumo-gastric as far as 

 the 7th cervical vertebra, where it passes 

 outwards and somewhat upwards into the 



Fig. 7. Nervous relations of the thoracic rete. The rete is dotted. Part of the posterior thoracic vein has 

 been omitted in order to show the nerves underneath. 



/, Pneumo-gastric nerve k, Retial ganglion 



g, Cervical sympathetic chord /, Phrenic nerve 



//, Thoracic sympathetic chord 

 /', Middle cervical sympathetic ganglion 

 j, Posterior cervical sympathetic ganglion 



a, Dorsal aorta 



b, Carotid artery 



c, Jugular vein 



d, Posterior thoracic vein 



e, Pulmonary artery 



cr 3 ~ B , Cervical spinal nerves 

 tr 1 ' 5 , Thoracic spinal nerves 



