THE THORACIC RETE 347 



body of the rete. In the middle of the retial mass it forms the middle sympathetic gang- 

 lion (Fig. 7 i) — a large stellate ganglion lying opposite the ist rib. Small sympathetic 

 nerves run from it into the body of the rete. The middle cervical sympathetic ganglion 

 receives rami from the 5th, 6th, 7th and 8th cervical and the ist thoracic spinal roots — 

 all those which form the cervico-brachial plexus. From the hinder part of the ganglion 

 there is given off a bundle of nerves forming a plexus whose components run above 

 and below the posterior thoracic vein (Fig. 7). On emerging from the body of the rete 

 they join up to form a pair of nerves passing to the heart and lungs. One of these has 

 a ganglion on its course — the retial ganglion (Fig. 7) — and receives a long ramus from 

 the 4th cervical spinal, from which the phrenic is also derived. The retial ganglion lies 

 a little behind and dorsal to the posterior thoracic vein and also gives off nerves into 

 the substance of the rete. Nerves also run into the rete directly from the cervical and 

 thoracic spinal roots — the most conspicuous being a stout retial nerve from the ist 

 thoracic, which ramifies among the retial capillaries in the neighbourhood of the 

 posterior thoracic vein. 



The posterior cervical sympathetic ganglion lies more dorsally within the retial 

 substance, close up against the heads of the 3rd and 4th ribs (Fig. yj). It is connected 

 with the middle ganglion by two stout chords : these have cross connections and really 

 form a short plexus. The posterior ganglion receives rami from the 2nd and 3rd thoracic 

 spinal nerves, and gives off yet a third sympathetic nerve to the heart and lungs, running 

 across the distal part of the aortic arch to reach its destination. The main thoracic 

 ganglionated chord leaves the posterior cervical ganglion and runs as usual across the 

 heads of the ribs forming segmental ganglia, each of which has the usual rami running 

 to the spinal roots. The ist of these segmental ganglia lies between the heads of the 

 4th and 5th ribs (Fig. 7). 



In the larger foetus there appeared to be communication within the rete between all 

 the spinal nerves contributing to the two sympathetic ganglia, and fibres could be seen 

 running from these spinal branches to the three sympathetic nerves to the heart and 

 lungs. The two sympathetic ganglia were very closely invested by the retial substance, 

 which formed a compact mass around them. 



From the above it appears that the rete is mainly under the control of the sym- 

 pathetic system, while to some extent it is evidently under the control of the somatic 

 as well. 



SUMMARY 



The thoracic rete is a network of vascular capillaries situated around the anterior 

 extremity of the thoracic cavity, in the fork formed by the convergence of the rectus 

 capitis anticus major and the scalene muscles passing to their joint insertion upon the 

 basis cranii. The rete is independent of surrounding structures, but in close contact with 

 the muscles of the first two intercostal spaces. 



The vascular networks extend along the vertebral column and between the heads of 



