NERVOUS SYSTEM 155 



et al. 1945), and the sensitivity of the gut is somew^hat increased by 

 eserine. The response is inhibited by atropine treatment. A 

 cholinesterase specific enzyme has been demonstrated in the gut 

 (Millott, 1943a) and presumably is the enzyme involved in 

 breaking dow^n internally produced acetylcholine. 



The synthesis of acetylchoHne by the gut nerves is shown by the 

 experiments of Ambache, Dixon and Wright (1945). The normal 

 peristaltic activity of the isolated intestine of Liimhricus and Allo- 

 lobophora is diminished by cooling to 0-7 °C, but the gut still 

 reacts to the addition of acetylcholine. The cooling action inter- 

 feres with normal acetylcholine production and thus inhibits the 

 intrinsic nervous activity of the intestine. Gut preparations kept in 

 saline in the presence of eserine at 17-20 °C release into the 

 medium substances capable of causing contraction of other similar 

 preparations. Alkali destroys this activity. 



Inhibition of the muscular movements of the intestine of 

 Liimhricus is also an active process (Wu, 1939 a, b; Millott, 1943 

 a, b). The responses of the gut to the addition of adrenaline 

 depends (a) upon which part of the gut is considered, and (b) 

 on the concentration of adrenaline used. The anterior portions of 

 the gut, buccal cavity, pharynx and oesophagus are stimulated to 

 contract by adrenaHne in all concentrations. On the posterior 

 portions of crop, gizzard and intestine adrenaline has two actions, 

 one inhibitory and one stimulatory depending upon the amount 

 added. Acetylcholine-induced contractions can be counteracted by 

 large dose levels of adrenaline. 



After cooling the gut adrenaline has no effect upon it and 

 Ambache et al. (1945) consider that this indicates that the usual 

 action of adrenaline is to potentiate the action of acetylcholine. 

 Ephedrin, used as an antagonist to adrenaHne in vertebrates, 

 slightly increases the actions of adrenaline in the earthworm gut. 

 Ergotoxin abolishes the action. Millott (1943b) injected adrenaline, 

 acetylcholine, tyramine and ephedrine into the blood stream of L. 

 terrestris through the pseudohearts, and found that the actions of the 

 nervous system could be mimicked. He concluded that the nerves 

 controlling the tone of the gut were cholinergic and adrenergic, 

 and that the two systems are antagonistic, not potentiating. Wu 

 (1939b) decided that the nerves arising in the septa were the 

 adrenergic variety, since their action was abolished by ergotoxin. 



