40 THE VITAMINS 



extract within a period of 6 to 12 hours, recovery must be a persistent 

 one for two or better three days, in order to establish the activity of 

 an extract. If the symptoms do not clear up, it is not proof of the 

 non-activity of an extract unless (a) the bird is strong, and (b) the 

 extract is administered within 12 hours from the start of the con- 

 vulsions if it is the first attack, and within three hours if it is the 

 second." 



As thus tested, the yeast concentrate before the final evaporation 

 to dryness was of such strength that 0.05 cubic centimeter cured the 

 usual pigeon of symptoms within six hours and kept it from 

 convulsions upon a diet of polished rice for about three and one-half 

 days. After evaporation to dryness 3 milligrams was required. The 

 extract did not lose its activity on treatment with an acid solution of 

 sodium nitrite, thus apparently excluding primary amines and many 

 secondary amines as responsible for antineuritic action. Negative, or 

 only temporary, results were obtained in curative tests with various 

 substances of basic character, including hexylamine, guanidine, and 

 dimethyl urea. The administration of histamine, however, produced 

 cures in a small percentage of cases. Peters was at a loss to explain 

 the occasionally curative action of histamine except by attributing it 

 to some temporary vascular action. 



In a later paper Kinnersley and Peters (1925) reported further 

 attempts at concentrating the active material obtained by the method 

 described in 1924 with the exception that treatment with barium sulfide 

 was omitted and the charcoal adsorption was applied to the acid fluid 

 after removal of the mercury precipitate. 



In testing the activities of their various preparations they adopted 

 as the standard of comparison: 



rr 1- ^- V /T- A ^ Number of days' protection after cure ., ,„„ 



Torulin activity (T.A.) = ..,.. — -. /. — -. X 100. 



Weight in mg. of the dry preparation 



Torulin, the term introduced by Edie et al. (1912), was defined as 

 "the principle in yeast which cures symptoms of head retraction in 

 pigeons induced by feeding upon polished rice." 



By successive treatments of the charcoal concentrate with ethyl alcohol to a 

 concentration of 60 per cent, 25 per cent lead acetate, methyl alcohol to a concen- 

 tration of not less than 90 per cent, 10 per cent "dialyzed iron," followed by the 

 rapid addition at room temperature or below of normal sodium hydroxide until 

 a precipitate ceased to form, and finally ethyl alcohol in increasing concentrations 

 followed by ether, an active fraction was obtained which was soluble in absolute 

 alcohol, and the activity of which varied from 50 to 100 T.A. The purpose of 

 this "rather empirical" fractionation method, the final stages of which required 

 much care, was to free the extract from gum and ash. The final treatment of the 

 fraction is described as follows : 



