COMPOSITION OF HUMAN MILK IN AUSTRALIA. 



195 



7. Percentage of fat in milk of each breast. 

 It has been supposed by certain investigators that there 

 is a constant difference between the average percentages 

 of fat in the milk obtained from each breast. Mendes de 

 Leon (loc. cit.) states that the milk of the right breast is 

 richer in fat than that of the left, while Zappert and Jolles 

 (1903) found the milk of the left breast to contain up to 

 0*6% more fat than that of the right breast. The samples 

 of milk examined in the present case have been compared 

 together to determine whether any such difference between 

 the secretions of the two breasts is to be seen in them. All 

 of the samples compared were of the milk secreted at the 

 same stage of lactation (4-5 days post partiim). The 

 average percentage of fat in the milk of the right breast 

 (19 samples) was found to be 2*57; the average percentage 

 of fat in the milk of the left breast (22 samples) was found 

 to be 2*50. In view of the large variations in the percentage 

 of fat in the samples of human milk examined, however, 

 the difference between these two figures (0*07%) is too small 

 to justify a conclusion that the average percentage of fat 

 in the milk of one breast is persistently higher than that of 

 the milk of the other breast. 



8. Effect of number of pregnancies on composition of 

 human milk. 



In the following table are given the average values of 

 the density and composition of the milk of women at the 

 first, second, third, and subsequent pregnancies. 



Table VII. — Effect of number of pregnancies on composition of 

 hum,an milk. 



Number or pregnancies 



1 



2 



3 



More than 3 



Number of samples 



46 



33 



20 



13 



Density ... 



1-0324 



1-0328 



1-0312 



1-0309 



Total solids 



12-2 



12-6 



12-6 



12-5 



Fat 



2-91 



3-04 



3-44 



3-32 



Solids not fat 



9-4 



8-6 



8-1 



9-1 



Protein ... 



201 



2-14 



2-17 



1-89 



Solids not fat nor protein 



7-4 



6-4 



6-4 



7-2 



