FEEDS AND FEEDING I467 



quite possible that the amount of exercise taken by the pigs, as determined 

 simply by the state of feeling induced by the ingested phosphorus com- 

 pounds, quite independently of the fundamental nutritive effects, may have 

 entered into the determination of the relative development and even into 

 the composition of the different parts. 



Certain differences observed in the composition of the tissues can be 

 attributed to variations in the liquid content of the parts, the salts varying 

 accordingly, or to the composition of the supporting structures, or the iin- 

 organised nutritive matters. 



While the hypophosphites, nucleic acid and ph>i:in have not been sub- 

 mitted to so complete a study as that devoted to the comparison of the 

 phosphates and glycerphosphates, no fact having led the writers to investi- 

 gate the question, they consider that when added in their ordinary " chemi- 

 cally pure " form to rations poor in phosphorus such as those studied, these 

 five compounds do not differ in their nutritive effects on the gross compo- 

 sition of the growth of the animals, except in so far as affected by the rela- 

 tive tolerance of the pigs towards these preparations and the consequent 

 influence on the spirits and activity of the animals. 



The writers think it possible to arrange the compounds in decreasing 

 order of toleration, thus : glycerophosphates, phosphates, ph>'tin, nucleic 

 acid (from beer-3'east) and hypophosphites, the compounds being adminis- 

 tered in doses containing equal amounts of phosphorus ; nevertheless the 

 order of the last two compounds is uncertain. It has not been shown that 

 these differences in acceptability were directly related to the fundamental 

 nutritive effects. If they have been established for the chemically pure 

 compounds thej^ certainly do not exist in foods containing these compounds 

 combined naturally. 



When phosphorus is added to a ration in the form of very soluble com- 

 pounds a much smaller amount will be tolerated by the animal than when 

 the phosphorus is supplied in its natural form in food. 



Owing to the great difficulty of making the animals eat the nucleic 

 acid, commercial phytin and the corresponding compound obtained from 

 wheat-bran, it is concluded that the isolation of such compounds from the 

 natural ])roducts, alters at least their therapeutic effects. So that it is 

 impossible to draw am' conclusion on the nutritive value of these compounds 

 present in ordinary food from experiments made with the pure extracted 

 substances. 



It has not been established that the organic compounds used in this 

 investigation have a higher feeding value than that of inorganic compounds 

 of phosphorus. No fundamental differences in the nutritive value of the 

 compounds of phosphorus studied were established. No basis therefore, 

 was discovered for a differentiation between the nutritive values of organic 

 and inorganic compounds of phosphorus generally. 



Even admitting debated siiperior nutritive value of organic phosphorus 

 compounds, there is no doubt that the quantity of organic phosphorus con- 

 tained in the body is a ver}' small part of the total phosphorus, and it is cer- 

 tain that in the diet of all omnivorous and herbivorous animals (i. e. of all 



