402 



SCIENTIFIC AGRICULTURE 



August, 1922 



more than twenty-four hours usually nulli- 

 fies its protective power as is the case with 

 all the sterilizing methods in use. It has 

 been determined by feeding experiments that 

 even where fresh milk is used it does not 

 protect unless it is consumed in quantities 

 so large that it must form the sole article of 

 diet. It is now the practice where milk is 

 used for infant feeding to fortify it with 

 pressed suede turnip juice. 



Experimental scurvy can he produced 

 upon guinea pigs most readily. A sole diet 

 of rolled oats, bran and water will produce 

 a typical case of scurvy in a few weeks. A 

 small quantity of autoclaved milk is also given 

 daily to ensure a supply of the fat soluble and 

 antineuritic factors and give a clinical pic- 

 ture of scurvy uncomplicated by other defi- 

 ciency di'seases. This method is used in 

 studying the antiscorbutic power of various 

 food stuffs, since these will prevent the 

 disease if active or if inactive indicate their 

 deficiency by the weigl)t curve of the animal 

 under observation showing a gradual loss fi- 

 nally ending in a typical case of scurvy. 



The fat soluble "A" factor derives its 

 name since it was discovered associated with 

 the ether soluble portions of egg yolk and 

 butter fat. -Alcohol-ether extracts of animal 

 tissues like the liver and kidney also indicat- 

 ed the presence of this compound. Earlier 

 attempts to separate it from its original 

 source in the plant tissue by expression or by 

 extraction with fat solvents proved negative 

 and it was presumed that it existed in the 

 plant cell in a combined form which was 

 hydrolyzed by the digestive ferments of the 

 animal and stored up with the animal fats. 

 Later researches demonstrated that alcohol 

 could remove it from plant tissues and this is 

 now a routine method of separating it from 

 these sources. 



It is soluble in alcohol, ether, benzene and 

 partly so in chloroform and carbon disul- 

 phide. It can readily be oxidized and lose 

 its activity either by shaking the molten fat 

 with warm water or blowing air or oxygen 

 through the liquid fat. If care is taken to 

 avoid the action of oxygen the molten fat 

 can be heated for hours and still' retain its 

 fat soluble accessory unimpaired. 



The principal sources of the fat soluble 

 factor in addition to those imumerated above, 

 are plant leaves which contain chlorophyll 

 and cod liver oil. This latter substance is 

 several hundred times more active weight 

 for weight than any other fat soluble bearing 

 material when fresh and crude but parti.illy 



or totally inactive after being subjected to the 

 usual refining methods. Vegetable oils on 

 the other hand are practically negative as 

 regards this valuable constituent, and con- 

 sequently butter substitutes which have these 

 as a base are likewise negative. The syn- 

 thetic power of the plant which produces 

 this factor is associated with the chloroi^hyll 

 since green cabbage leaves and green algae 

 are fairly potent while the inner white leaves 

 of the cabbage and red algae have proved neg- 

 ative upon biological examination. Plants 

 can produce the "A" factor when grown upon 

 artificial media free of this element and Avill 

 go on with the synthesis even when the chloro- 

 ])hyll-bearing area is trimmed off and allowed 

 to grow again, but it does not appear till 

 etiolation of the seedling is well under way. 

 When these experiments are carried out 

 under conditions which prevent the develop- 

 ment of chlorophyll, such as growing them in 

 a dark room, the fat soluble element is pres- 

 ent only in the merest traces being negative 

 for all practical considerations. 



This factor is usually associated in natural 

 food stuffs with the yellow xanthophyll plant, 

 pigment carrotene, and this has been used as 

 a measure of the fat soluble content of the 

 material in question with a fair degree of 

 success. Several attempts have been made 

 to identify it with the coloring pigment. 

 However, butter is quite active even when 

 prepared from milk free from carrotene and 

 hens can be dieted to produce an egg with 

 a carrotene free yolk and such eggs can be 

 hatched out successfully. Even butter can 

 be made carrotene free by dissolving in al- 

 cohol and removing the pigment with animal 

 charcoal and still retain its original curative 

 and preventive powers. Finally pure carro- 

 tene preparations have shown no demonstra- 

 ble activity similar to that displayed by the 

 fat soluble factor when administered to test 

 animals. 



The various fats have been systematically 

 examined to ascertain the source of the acces- 

 sory function. When subjected to hydrolysis 

 by alkali in an atm()s])Iicre of carbon dioxide 

 the fatty acid and glycerol fractions have 

 not identified themselves as the therapeutic 

 element which is obtained by making an ether 

 extract of the residue and this is found to 

 contain the vitamin along with the unsaponi- 

 fiable fraction of the fat mixture. This 

 method has yielded liighly concentrated and 

 vcrv {)otent |)rt'parations of the A factor. 



'i'he function of tliis accessory in the meta- 

 bolic cvcle is larffclv concerned with the cal- 



