WHEN THE MOTHERS FAIL 37 



subtle and important changes as the digestive tract 

 of the infant changes in the course of its develop- 

 ment. 



It is for this reason that, in its natiural state, the 

 milk of one species is, in a sense, poison to any other 

 species. Anything but maternal milk is a foreign 

 substance in the digestive tract of an infant, liable 

 to cause serious irritation and disorder; but when 

 maternal milk cannot be had, if we are to prevent 

 starvation and death, something else must be used, 

 and an endeavor made to have that substitute as 

 little poisonous as possible. Thus it is that the 

 physiological chemist must set himself to the task of 

 finding a food as closely resembling human mother's 

 milk as possible at every stage of the child's growth 

 so as to carry on artificially the work which Nature 

 does in making blood, tissue, bone, and nervous energy. 

 The digestive tract of a baby is a wonderful factory, 

 where these processes are carried on by Nature by 

 means of automatic machinery; and when Nature 

 fails, man must assume the delicate task of carrying 

 on the work by other and clumsier methods. 



It is not impossible, nor even very unlikely, that 

 in the course of a few generations artificial feeding 

 of infants will be the rule in civilized countries and 

 breast-feeding practically unknown.^" The evolu- 

 tion of the species proves that Nature is wonderfully 

 adaptable, and there is no reason to fear that the 



