NERVES OF THYROID AND PARATHYROID BODIES 99 



In most instances the nerves can be traced along the vessel 

 wall, within which are also found their few terminal branches. 

 A few other fibers are present which cannot be followed along a 

 vessel, but which seem to run in the connective tissue between the 

 groups and cords of gland cells. It is probable, however, that 

 these accompany smaller vessels which are too poorly stained to 

 be visible. I am of the opinion that the nerves are entirely vaso- 

 motor for the supply of the blood vessels, and that there are no 

 special glandular or secretory nerves in the parathyroid, because 

 none of the fibers leave the supporting connective tissue and pene- 

 trate into the cell groups. 



CONCLUSIONS 



1. The nerves of the thyroid are entirely non-medullated and 

 reach it from the cervical sympathetic ganglia by following the 

 thyroid arteries. 



2. In the thyroid there are formed elaborate nervous plexuses 

 around all the blood vessels and all the follicles, the nerves form- 

 ing the latter coming from the plexuses surrounding the smaller 

 arteries. 



3. The perivascular nerves end in the walls of the blood vessels 

 and furnish the vaso-motor supply, while those of the perifollicu- 

 lar plexuses end on the bases of the epithelial cells and probably 

 carry impulses influencing secretion. 



4. All the nerves are varicosed but do not anastomose. 



5. The nerves of the parathyroid come from the same set that 

 supplies the thyroid and pass into it along with the branches from 

 the thyroid arteries. These nerves probably all end in the vessel 

 walls and are vaso-motor in function. 



6. No ganglion cells are found in either the thyroid or para- 

 thyroid bodies. 



