174 H. S. H. WARDLAW. 



The total solids of the milk were determined on 1 cc. 

 measured from a pipette and evaporated to dryness on a 

 watch-glass in a glycerine oven at 103° O. This small 

 quantity of milk can be spread out in a thin layer on the 

 watch-glass and dries fairly quickly at 103° 0. In the 

 calculation of the percentage of total solids the volume of 

 the milk is multiplied by its density to give the weight. 

 The values of the percentage of total solids are given to 

 one part in one hundred. 



The fat in the samples of milk was determined by the 

 Rose-Gottlieb (1888, 1891) method. In this method the fat 

 is extracted from the milk mixed with alcohol and ammon- 

 ium hydroxide by means of a mixture of ether and petroleum 

 spirit of low boiling point, the fat dissolved in this mixture 

 being weighed after evaporating off the spirit. The results 

 of the analyses are given to one part in one hundred. 



It has been stated by Radenhausen (1881), Forster (1881), 

 Mendes de Leon (1881), and by others, that the percentage 

 of fat in human milk is lower in the portions first withdrawn 

 than in the portions withdrawn later, and Reyher (1905), 

 Forest (1906), and Bngel (1906) have suggested that on 

 account of this fact the whole of the milk contained in the 

 mammary gland should be taken for analysis in order to 

 determine the average percentage of fat in it, or, failing 

 this, that equal portions should be taken for analysis at 

 the beginning and the end of the withdrawal of the sample, 

 the mean of the percentages of fat found in these two por- 

 tions being taken as the average percentage of fat in the 

 total amount of milk withdrawn. Helbich (1912), who 

 reinvestigated this question later, did not find this depend- 

 ence of the percentage of fat in human milk on the volume 

 withdrawn from the breast, however. He therefore states 

 that the inverse relation between volume and percentage 

 of fat which Engel claims to have observed, does not exist. 



