INTRODUCTION 



was essential for the growth and lactation of rats and the latter con- 

 firmed the observations of previous workers that rats fed a diet low 

 in choline, even though supplemented by aneurine and riboflavine, 

 developed fatty infiltration of the liver. The addition of pyridoxine 

 resulted in the formation of necrotic renal lesions, similar to those 

 encoimtered in cystine intoxication. The severity of the lesions was 

 reduced by substituting egg white for sucrose in the diet. This 

 increased the methionine : cystine ratio, which had already been 

 shown ii» ^2 to affect fatty liver formation, an excess of cystine favour- 

 ing and an excess of methionine preventing fatty livers. Administra- 

 tion of choline prevented the renal changes and also sometimes exerted 

 a lipotropic effect. 



Shortly afterwards, choline was shown ^^ to be essential for growth 

 and prevention of perosis in growing chicks, although choline-deficient 

 chicks had not developed fatty livers at four weeks of age, and bone 

 phosphatase values were normal in chicks suffering from perosis due 

 to choline deficiency. 



The formation of renal lesions in young rats on a choline-deficient 

 diet was confirmed by W. H. Griffith and D. J. Mulford ^* who showed 

 that the non-protein nitrogen of the blood was also increased. The 

 possibility of survival and renal repair depended on the severity of 

 the lesions. Most members of the vitamin B complex were without 

 effect on the severity of the symptoms, but nicotinic acid had a slight 

 beneficial effect. 



In spite of the strong resemblance between the behaviour of choline 

 and that of other vitamins in animals, there has been considerable 

 hesitation about accepting choline as a vitamin. One difficulty is 

 that it occurs in the body in such large amounts, compared with other 

 members of the vitamin B complex (with the possible exception of 

 inositol, page 564) as to suggest that it is a structural component of 

 the body rather than a metabolic catalyst. Moreover, relatively 

 enormous amounts are normally ingested by animals and humans, 

 the daily requirement being estimated at 35 to 100 mg. per kg. of 

 bodyweight for different species of animals (page 594) compared with 

 a daily requirement of only 15 to 30 /xg. per kg. of bodyweight per day 

 of aneurine or riboflavine. 



The demand for choline exceeds even that of inositol (page 576) 

 and is actually of the same order as the requirement for certain amino 

 acids. Inositol and choline may usefully be considered as links con- 

 necting the vitamin B complex proper with the amino acids, inositol 

 being more closely related to the vitamin B complex and choline to the 

 amino acids. 



Another possible argument against the inclusion of choline in the 

 vitamin B complex is that it has never been shown to be associated 



583 



