56 THE SECRETIONS: 



for determining the goodness of the milk by a microscopic ex- 

 amination, is founded on incorrect principles ; he assumes that 

 the increase of the butter and of the other constituents is 

 simultaneous ; an assumption that the above analyses show to 

 be inconsistent with facts. 



Changes in the milk, corresponding with the age of the infant. 



It seems probable that certain changes will be observed in 

 the milk when the progress of development of the child indicates 

 the necessity for other food. The question is one of consider- 

 able physiological interest, and in order to elucidate it I made 

 analyses of the milk of a woman during a period of nearly six 

 months, commencing with the second day after delivery, and 

 repeating my observations at intervals of eight or ten days. 



The results would doubtless be more decisive if the expe- 

 rimentalist were able to exclude all disturbing influences : but 

 in almost all cases the exercise of a strict control over the 

 method of living and the nature of the food of the mother, is just 

 as impossible as the exclusion of exciting moral forces. 



The fourteen analyses (the colostrum being excluded) gave 

 the following results : 



A glance at the three columns of casein, sugar, and butter, 

 will show that, with few exceptions, 1st, the quantity of casein 

 is at its minimum at the commencement ; it then rises consi- 

 derably, and ultimately attains a nearly fixed proportion ; that, 



