ANEURINE (thiamine) 



With pure aneurine, the duration of cure increases with increasing 

 dosage and is linear over a considerable range, so that aneurine pre- 

 parations can be assayed by comparing the duration of cure resulting 

 from the test dose with that of a dose of standard. 



Other criteria besides duration of cure have been used with the 

 rat curative method, e.g. the time required for the rat to return to the 

 weight it had when the vitamin B^ injection was given ^^ and the 

 number of day doses per gram of material,^^ analogous to the pigeon 

 method. 



Bradycardia and Convulsion Methods 



T. W. Birch and L. J. Harris ^' compared Smith's method with 

 two other methods in which the rat is used. The first of these, the 

 bradycardia method, is based on the observation that the heart rate 

 of the vitamin B^-deficient rat is lower than that of the normal animal, 

 but is increased on administration of vitamin B^, the increase being 

 proportional to the dose given. Thus the heart-beat of a rat fed on a 

 vitamin B^-deficient diet for three weeks is measured by means of an 

 electrocardiograph, and again twenty-four hours after giving a single 

 measured dose of the test solution. The result is compared with 

 that obtained after the administration of known amounts of a standard 

 vitamin preparation to control animals. 



The second method depends on the cure of convulsions which 

 develop in rats fed a diet almost, but not quite, free from aneurine. 

 The number of days which elapse between the administration of the 

 test solution and the onset of the next convulsion is taken to be a 

 measure of the amount of vitamin present. Birch and Harris re- 

 commend the bradycardia method as being quicker and easier than 

 the other methods and as being no less reliable ; they have used it 

 extensively, but in the hands of other workers it has not given good 

 results. 



B.P. Method 



The weight method is the method of assay most widely employed 

 in this country and the one adopted as official in the Addendum 

 1936 to the British Pharmacopoeia 1932. About ten young rats, each 

 weighing 40 to 50 g. , are fed immediately after weaning on the following 

 basal diet, which is cooked by steaming for about three hours : 



Sodium caseinate . 



Rice starch 



Arachis or cottonseed oil 



Salt mixture 



Water . 



100 g. 



300 g. 

 75 g- 

 25 g. 



500 g. 



30 



