122 COMPARATIVE PHYSIOLOGY 



not confined to muscles which have a sympathetic innervation ; 

 and the validity of arguing that an effector organ such as a 

 melanophore possesses a sympathetic nerve supply from the 

 fact that it is acted upon by adrenaline, may be questioned. 

 Adrenaline has a powerful action on both the ganglion and 

 heart-muscle in Limulus (Carlson), the heart of the crab 

 Maia (Hogben and Hobson), and the intestine of the crayfish 

 (Ten Cate). It also acts in very great dilution as an excitant 

 to the plain muscle of molluscs and annelids, as illustrated 



Pjg, 31.— Action of adrenaline on the crop of Aplysia. 



by the oesophagus of Aphrodite and Aplysia (Hogben and 

 Hobson) and of Helix (Ten Cate), also the heart of Pecten 

 (Hogben and Hobson) . The poison with which the cephalopod 

 kills its crustacean prey is a natural base, tyramine (CgHpH.- 

 CH2CH2NH2) of closely allied structure to adrenaline 

 (CeH3(OH)2CH.OH.CH2NH.CH3) and to certain other 

 phenolic amines for which Barger and Dale^ have described 

 a similar physiological action on mammalian tissues. In 

 this connexion it is interesting to note the presence of adrenaline 

 in the salivary glands of a toad {cf. Chapter III). 



