96 DARMON A. RHINEHART 



size. From the perivascular plexuses of these smaller arteries 

 are given off here and there nerves which penetrate into the inter- 

 follicular connective tissue for a greater or lesser distance and 

 form the perifollicular plexuses. These branches are almost 

 always single fibers, for none of the larger nerves leave the ves- 

 sels as such. 



The perifollicular plexuses completely surround all of the fol- 

 licles of the thyroid, or, as Anderson has said, there is present a 

 diffuse plexus of nerves in which the follicles seem to be imbedded 

 (fig. 3) The nerves coming from the perivascular plexuses may 

 supply a follicle near the artery, they may supply one at a con- 

 siderable distance, or their branches may enter into the formation 

 of the plexuses of several follicles. These nerves divide again and 

 again into a large number of fine, varicosed fibers which completely 

 surround a single follicle or adjacent follicles in a dense nervous 

 network. There is absolutely no regularity, arrangement or 

 method in the place or manner of branching, nor in the direction 

 the branches may take after leaving the main stem. Neither is 

 there any regularity in the distribution of the glandular nerves, 

 nor anything that can be said of their distribution, except that 

 they enter into the formation of the plexuses around one or more 

 of the follicles of the thyroid. There are no primary or secondary 

 plexuses, as described by Berkeley, but a single one surrounding 

 each follicle. 



In regard to the anastomoses of the nerves of these plexuses 

 the same statement applies that was made in regard to the peri- 

 vascular nerves. In the thinner sections the nerves can all be 

 traced as individuals, and the branches can be traced to the parent 

 stem if it is included in the section. 



The perifollicular nerves are also very varicosed, the varicosi- 

 ties corresponding in size and shape to those found on the nerves 

 of the perivascular plexuses. 



Perhaps the most important fact to be determined concerning 

 the nerves of the thyroid is the position and manner of the final 

 endings of the follicular nerves, for the effect of nervous impulses 

 on the secretory activity of the gland cells would depend, to a 

 great extent, on the intimacy of the relations of the nerves to them. 



