§ 2.114 SECRETORY CELLS FROM THE NERVOUS SYSTEM 33 



Gland cells of the corpora cardiaca 



The CORPORA CARDIACA are not only storage organs for neuro- 

 secretion from the cerebrum but they are also endocrine organs in 

 their own right. Together with the corpora allata (§ 2.122) they 

 lie dorsal to the oesophagus and form the retrocerebral system 

 (Fig. 2-8), the form of which varies in different insects; both 

 organs may be paired, or one or both may be fused in the mid-line. 



Together with some nerve cells, connective tissue and tracheae, 

 loosely packed secretory cells form the bulk of the corpora car- 

 diaca and produce the intrinsic secretion of this organ (§ 3.111). 

 Like the sympathetic cells of the hypocerebral ganglion, these 

 cells arise from the stomodaeal ectoderm and are undoubtedly 

 nervous in origin, although they have become so much specialized 

 for secretion that they have lost most of the characters of neurons, 

 notably the axons of typical neurosecretory cells (Figs. 2-\e and 

 2-9a). These cells are rich in ribonucleic acid and reveal a Golgi 

 apparatus after suitable treatment. With haematoxylin chrome 

 phloxin, their secretion stains quite distinctively from the neuro- 

 secretion, the former having a greater affinity for phloxin and the 

 latter for haematoxylin (de Lerma, 1956). 



2.114 Neurosecretory systems and glands of Vertebrata 



There are two main sources of hormones that are derived from 

 the vertebrate nervous system. One is a set of neurosecretory cells 

 in the hypothalamus of the brain with their storage-and-release 

 organ (akin to the sinus gland of the Crustacea) in the neuro- 

 hypophysis. The other is an aggregation of gland cells that are 

 derived from sympathetic ganglia and form the suprarenal body 

 of fish and the adrenal medulla of tetrapods. 



Neurosecretory cells of the hypothalamus and the neurohypophysis 

 It is now well established that the hormones of the neuro- 

 hypophysis (or posterior lobe of the pituitary body) are not secreted 

 within that body but by neurosecretory cells in the hypothalamus 

 of the brain. The cell bodies are grouped together in the preoptic 

 nucleus in fish and amphibians and separated into two groups, 

 the supraoptic and paraventricular nuclei, in reptiles, birds and 



