EXPERIMENT STATION RECORD. 



Vol. YIII. I^o. 4. 



The error involved in calculating- the protein in feeding stuffs by mul- 

 tiplying the nitrogen content by the factor 6.25 has been niucli discussed 

 by chemists, and, together Mith the methods of determining other con- 

 stituents, has been so severely criticised -by them as to cause many lay- 

 men to distrust the reliability of fodder analyses in general. The present 

 calculation of protein is, of course, based on the assumption that the 

 proteid bodies in pure state contain, on an average, IG i)er cent of 

 nitrogen. This average was fixed upon over forty years ago, when the 

 Weende method for fodder analysis was being elaborated. The nitrog- 

 enous constituents of plants have always been among the most difficult 

 substances to study chemically, on account of the difficulty in getting 

 pure preparations of them. At the time the average was adopted it 

 probably represented the best knowledge that was to be had regarding 

 their composition. But as investigation of these bodies has progressed 

 it has become evident that the average was not reliable, in case of cer- 

 tain materials at least, and numerous suggestions have been made for 

 modifying the factor. 



As early as 1872 Professor Eitthausen, in his book on The Albumi- 

 noid Bodies of Cereals, Legumes, and Oil-bearing Seeds,' called atten- 

 tion to the apparent inaccuracy of tlie factor, as he had found that 

 most proteid bodies which had been examined- contained more than 16 

 per cent of nitrogen, and some as high as 18 per cent. He recom- 

 mended that 6 be used as the factor in the case of the seeds of cereals, 

 most legumes, and oil-bearing seeds, and 5.5 in the case of lupine seed 

 and certain press cakes. 



This suggestion has been adopted by only a few chemists, although 

 the desirability of a change has been frecpiently discussed. What is 

 perhaps the most forcible argument in favor of a change comes from 

 this same author in an article in a current periodical, abstracted else- 

 where (p. 279). Professor IJitthausen has taken pains to compile all 

 the analyses available to him of proteid bodies isolated from various 

 seeds and oil cakes used as feeding stuffs, and presents these in his 

 article. 



'Die Eiweisskorpt^r <ler Getreidearton, Tliilseiifriifhte iind Oelsameii. p. 236. 



269 



