62 THE SIMPLER NATURAL BASES 



(Franchini [1908]). Muscarine, neurine and betaine, on the other 

 hand, are at least partially eliminated in the urine, and in this respect 

 choline behaves like an amino-acid unit of protein. Whether choline 

 is oxidised or whether it is synthesised into phosphatides is not known, 

 but the latter alternative is in agreement with the conception of choline 

 as a unit (Baustein) of phosphatides. The formation of choline in seed- 

 lings has been referred to above and its behaviour towards micro- 

 organisms is mentioned in the appendix. 



Riesser [1913 ; Ch. V, creatine] has recently carried out some ex- 

 periments which suggest that choline, when injected subcutaneously, 

 may be partially converted into creatine. In some rabbits he increased 

 the muscular creatine content 10-15 P 61 " cent, by this means. Riesser 

 supposes that choline condenses with urea according to the following 

 equation : 



NH 

 CHjOH / CH 2 OH NH, 



I + CO = I / 



CH 2 . N(CH S ) 3 OH N^ CH 2 > N(CH S ) C +2 CH 3 OH 



NH a \ NH 



and that the alcoholic group of the condensation product is then 

 oxidised to a carboxyl group, yielding creatine. The choline must 

 therefore lose some of its methyl groups, and in support of this theory 

 Riesser quotes an experiment in which choline chloride is carefully 

 heated with sodium tellurite and sodium formate (the latter salt acting 

 as a reducing agent) ; the garlick-like smell of methyl telluride is pro- 

 duced ; see also p. 77. 



The physiological action of choline has been studied by Gaehtgens, 

 and by Boehm [1885, 2] who observed salivation, myosis, and diastolic 

 arrest of the heart ; in frogs Boehm obtained general paralysis with 

 O'O25-O'i grm. ; in mammals croi-O'O2 grm. injected intravenously 

 gave a rise of blood pressure. The action is somewhat analogous to 

 that of pseudo-muscarine (synthetic " muscarine "). Brieger [1885, I, 

 p. 38] found that the toxic action of choline is inhibited by atropine 

 (" in pracisester Weise "). 



A detailed study of the action was made by Mott and Halliburton 

 [1899], who found that small doses of choline injected intravenously 

 cause a fall of blood pressure, but after a preliminary dose of atropine 

 a rise occurs. 



The antagonism between choline and atropine has been confirmed 

 by all subsequent investigators, but a good deal of confusion and con- 

 troversy has resulted from a statement by Modrakowski [1908] that 

 pure choline always produces a rise of blood pressure and that the 



