406 LECTURE XVII. 



there will be, necessarily, disadvantageous results. The value of any milk 

 substitute should in no case be determined by the fact that it contains 

 all of the elements required, nor by the fact that it contains in abundance 

 something (e.g., albumin, lime or phosphorus) which we are accustomed 

 to regard as especially essential. It is of chief importance that there is 

 nothing present in quantity below the required minimum. Even though 

 a milk substitute may be rich in phosphorus, it may be of but little value; 

 for, in order that the cells may utilize this phosphorus, it is necessary that 

 a sufficient amount of certain other substances should be present. This 

 shows where the greatest emphasis is to be placed. There is no question that 

 the unsuccessful results obtained in the artificial feeding of infants have been 

 due chiefly to the non-observance of this principle. It is obvious that 

 the mother's milk can never be replaced satisfactorily by some other 

 milk, or milk-substitute. This accounts for the greater mortality among 

 " bottle babies " than among those that are breast-fed. It is our duty 

 to make it generally known that on the one hand there is no perfect sub- 

 stitute for the mother's milk, and on the other hand to show that when 

 a replacement is unavoidable, the food should be adjusted in accordance 

 with the requirements established as a result of biological investigation. 



Chlorine is also an important constituent of milk. It occurs as chloride 

 of sodium and of potassium, and is distributed throughout all the cells of 

 the body. The alkali chlorides, especially the sodium compound, play 

 an important part in the formation of the urine. We shall come back 

 again to the relations of chlorides to the juices of the stomach. 



Finally, milk contains another element, sulphur, which is present in 

 a firm state of combination in the proteins casein, albumin, and globulin. 

 In this connection the reader is referred to what was said concerning the 

 decomposition products of protein. 1 



As far as we know, this comprises all the elements contained in milk. 

 It is, to be sure, possible that other elements are present in small amounts. 

 Thus, it has been suggested that milk may contain iodine. This assump- 

 tion was made merely because iodine plays an important part in the 

 economy of the cells. It is, however, perfectly possible that the new- 

 born child either contains iodine already stored away, or else that it makes 

 use of what it has only for later functions. 



There has been a great deal of discussion as to whether the animal 

 organism normally contains arsenic. It is certain, however, that if such 

 be the case, the amount present is extremely small. The question con- 

 cerning the arsenic content is an old one, and has been zealously discussed 

 by toxicologists in medical jurisprudence. 2 The contradictory results 

 concerning the normal occurrence of arsenic in the thyroid gland is prob- 



1 Cf. Lecture VIII, p. 157. 



3 M. Orfila: Traite" de me"decm tegal, 4th edition, Vol. Ill, part I, p. 285 (Paris, 1848). 



