§2.111 SECRETORY CELLS FROM THE NERVOUS SYSTEM 21 



as the hormone. The carrier may be some large molecule, like a 

 protein, which helps to anchor the smaller hormone molecule in 

 the cell until the time for its release. The hormone is then separ- 

 ated from the carrier, and apparently becomes free to enter the 

 blood and be passed on to the tissues. The carrier is usually 

 visible in the living cells by dark-ground illumination because of 

 its highly refractile granules which show up as bright spots (Fig. 

 2-3) ; in fixed preparations the carrier often stains, in a character- 

 istic but not specific way, with Gomori's chrome haematoxylin 

 phloxin and other stains, such as Mallory's triple stain for connec- 

 tive tissue (Scharrer and Scharrer, 1954a). 



There is increasing evidence that neurosecretory cells not only 

 secrete a greater quantity of some active chemical substance than 

 do typical nerve cells, but that they may also be specialized to 

 produce a greater variety of substances than just the acetylcholine 

 or adrenaline and noradrenaline of nerve endings. Recently, five 

 distinct staining reactions have been found among the neuro- 

 secretory cells terminating in the sinus gland of a crab (§2.112; 

 Potter, 1954), and it seems likely that eventually these will be 

 found to be related to separate hormones. 



The occurrence of neurosecretory cells, which release hormones 

 that have either kinetic or metabolic actions, is given with the 

 other sources in Table 3. The last column shows the later 

 sections of the book in which examples of these actions are des- 

 cribed. A more detailed summary of the occurrence of neuro- 

 secretion in invertebrates can be found elsewhere (Gabe, 1954). 



2.111 Epistellar body of Cephalopoda 



In most octopods there is a small compact body on the outer 

 surface of the stellate ganglion in the mantle cavity. In Eledone 

 moschata it is yellow and about the size of a pin's head. Micro- 

 scopic examination shows this epistellar body to contain a group 

 of neurosecretory cells (Fig. 2-\d) with their axons converging on 

 a central cavity, which contains secreted granules in a homo- 

 geneous ground substance. The granules presumably release a 

 hormone into the adjacent artery; but its ability to stimulate 

 muscle tone in the mantle (§ 3.12) has only been postulated from 

 extirpation experiments 



