132 



PERIPHERAL NERVE TERMINATIONS 



In its course through the core, the nerve fibre gives off fine lateral 

 twigs (Sala, Retzius). 



The connective tissue sheath consists of a granular protoplasm 

 which is permeated by densely felted spiral fibres (Sala) and is 



divided into ten to fifty concentric 

 lamellae by lines of flattened connect- 

 ive tissue cells and fibres. Accord- 

 ing to Schwalbe, however, these cells 

 form an endothelial coat on either 

 surface of each lamella. Pacinian 

 corpuscles are occasionally com- 

 pound, two or more adjacent cor- 

 puscles being supplied by branches 

 of the same nerve fibre. 



Pacinian corpuscles are found in 

 large numbers in the subcutaneous 

 tissue of the finger tips and of the 

 penis, as well as in the skin of other 

 parts, in the mesentery and the con- 

 nective tissue of neighboring organs 

 (e. g., the pancreas), in the pre verte- 

 bral connective tissue of the abdomen 

 and mediastinum near the walls of 

 the large blood vessels, in the serous 

 membranes pleura,pericardium,per- 

 itoneum in the peri-articular con- 

 nective tissue and periosteum, in the 

 sheaths of the larger nerve trunks, 



and in the connective tissue of the thyroid gland and of the 

 skeletal muscles. 



The corpuscles of Herbst (Key-Retzius corpuscles) are similar 

 in structure to the Pacinian corpuscles except that the core which 

 surrounds the axial nerve fibre contains cuboidal tactile cells. 

 They occur only in the cere of aquatic birds. 



The corpuscles of Grandry (MerkeVs corpuscles), also found 

 only in aquatic birds, contain several tactile cells of ectoblastic 

 origin similar to those found in the epidermis. Each cell is in 

 relation with a ring or meniscus formed by the expanded end of 

 a nerve fibre. The whole is included within a thin connective 

 tissue capsule and may be regarded as a compound tactile cell oc- 

 curring in connective tissue. 



FlG. 132. A PAPILLA OF THE DUCK'S 

 TONGUE, CONTAINING A CORPUS- 



CLE OF GRANDRY. 



The corpuscle contains four large 

 cells, between which are the tactile 

 menisci of the nerve ending. n, 

 nerve. Highly magnified. (After 

 Merkel, from Kolliker.) 



