ENDOCRINE CO-ORDINATION 123 



The adrenaline-secreting cells of the medulla have a close 

 ontogenetic relation to the post-ganglionic nerve cells of the 

 chain ganglia of the sympathetic nervous system ; unlike 

 other glands the adrenals are innervated by pre-ganglionic 

 fibres. Owing to the characteristic chrome-staining reaction 

 discovered by Henle their distribution has been studied in a 

 number of groups. In the lower vertebrates chrome-staining 

 cells often occur in the chain ganglia of the sympathetic 

 nervous system, and in elasmobranchs there are paired chromo- 

 phil bodies associated with each pair of ganglia, the cortex 

 of the mammalian gland being represented by a separate 

 structure, the interrenal body. Gaskell (19 14) has described 

 chrome-staining cells in the ganglia of Leeches and of those 

 Polychaetes which have a well-developed musculature in 

 connexion with the blood-vessels. These chromophil cells 

 are, according to Gaskell, the cell-bodies of those efferent 

 neurones which supply the vascomotor system. Gaskell 

 regards them as the common ancestral representative of both 

 the adrenalin-secreting cell and post-ganglionic neurone. 

 He obtained from extracts of the sympathetic ganglia of the 

 leech an action like that of adrenaHne on the mammaHan uterus. 

 Adrenalin-secreting cells have also been described in the 

 mollusc. Purpura^ by Roaf. In view of the widespread action 

 of adrenaline in the animal kingdom its distribution and possible 

 function in invertebrates are problems which would well 

 repay investigation. 



The Role o£ Adrenaline in Reptilian Colour-response.— Apart 

 from the indications provided by the work of Cannon in 

 favour of the view that excitement phenomena in the mammal 

 are associated with the Hberation of adrenaline into the blood- 

 stream, the only evidence for the functional activity of the 

 adrenals so far available is to be drawn from the study of colour- 

 response in the reptile. The early experimental work on 

 reptilian colour-response centred round the bionomic aspect 

 of the problem, more especially in correcting erroneous 

 teleological descriptions of protective colour- change in the 

 chameleon prevalent at the time and still widely credited. We 

 shall here consider the phenomena of colour- response in the 



