18 The Composition and Food Value of Bread. 



of the tissues of the body. In this respect, therefore, brown 

 bread appears to be preferable, but before definitely stating 

 thi-i as a fact it is necessary to know how much phosphoric 

 acid per day a man requires, and if the ordinary average diet 

 supplies that amount. 



Information on these points is not very abundant, nor are 

 the conclusions of the several investigators who have studied 

 the question very concordant. It appears, however, to be 

 fairly certain that an average man requires somewhere between 

 two and three grams of phosphoric acid per day. Analyses 

 giving the average percentage of phosphoric acid in common 

 articles of diet are not numerous, but from the sources 

 available I have estimated as best I could the amount of 

 phosphoric acid contained in the daily dietary of the average 

 working man as given in Table I. Assuming that all the 

 bread in his diet is made from straight grade flour containing 

 the average percentage of phosphoric acid given in Table III., 

 the daily consumption of phosphoric acid works out at 2'4 

 grams. If all the bread and flour is replaced by 80 per cent, 

 flour containing 'Sd per cent, of phosphoric acid, the daily 

 consumption of phosphoric acid becomes 3'2 grains. This 

 amount would certainly be enough ; indeed, thei*e appears 

 to be no reason to doubt that the smaller amount of 2*4 grams 

 is sufficient. It is sometimes stated that inorganically com- 

 bined phosphoric acid cannot be utilised by the tissues although 

 it may be absorbed from the intestine. The results of recent 

 investigators are usually quoted in support of this statement, 

 but I have not seen any writer on the subject quote the first 

 definite work on the utilisation of phosphoric acid which 

 has always seemed to be most conclusive. In this Journal for 

 the year 1853, Vol. XIV., page 451', Lawes and Gilbert describe 

 the results of their experiments at Rothamsted on pig feeding. 

 One of the lots of pigs in the experiment was fed entirely 

 on maize. After the first fortnight, during which the young 

 pigs had done very well, the maize-fed pigs began to go wrong. 

 Swellings appeared on the neck, and their breathing became 

 difficult. Maize is well known to be deficient both in protein 

 and in phosphoric acid. It was decided to supplement the 

 diet of maize meal by 3 o/. per head per day of a mixture 

 of finely sifted coal ashes, common salt, and superphosphate 

 of lime. The pigs readily ate this mixture, when their 

 abnormal symptoms at once disappeared. Afterwards they 

 increased iiormally in weight, and throve as well as many 

 of the other lots. It seems difficult to believe that any 

 constituent except the superphosphate can have been respon- 

 sible for this striking result, and if this is so, it is a striking 

 instance of the utilisation by the body of phosphorus in 



