§ 2.112 SECRETORY CELLS FROM THE NERVOUS SYSTEM 27 



verge on a half open cavity in communication v^ith the adjacent 

 blood sinus. In the blue crab, Callinectes, there is evidence that 

 the sinus gland is composed of as many as five groups of axon 

 endings, each with a distinctive staining reaction, which can be 

 traced back along the axon (Potter, 1954). It seems highly prob- 

 able that these groups are responsible for secreting and releasing 

 most of the specific chemicals with different hormonal actions, 

 which can be found by experiment in the sinus gland. 



NPMT' 



Fig. 2-7. Neurosecretory cells (NSC) in the ganglionic-X-organ 

 of a crab, Sesarma. Stained granules of secretion (G) pass down 

 the axons (SGN) to the sinus gland. Some cells (CB) have few 

 granules, others (RC) are almost depleted of granules. Small 

 ganglion cells and nerve fibres (NPMT) of the surroundmg ter- 

 minal medulla are also shown (from Enami, l^.-^l). 



