641 
Former analyses have for the most part assigned a higher amount 
of proteid and a lesser amount of sugar than this. The composition 
of milk is pretty nearly constant throughout lactation, except during 
the first month and toward the close. At the commencement of lac- 
tation the proteids and salts are high, and near its end the proteids 
have a tendency to diminish (Adriance). 
Proteids . — Our knowledge of the proteids of woman's milk is still 
incomplete. The most important proteid substances, however, are 
casein and lactalbumen. Some investigators mention a third, lacto- 
globulin. The casein is in chemical combination as calcium casein, 
and owing to its relative proportions to the other proteids is only 
slightly precipitated by dilute acids and not appreciably coagulated 
by rennet. 
The lact albumen is believed to be similar to serumglobulin. 
The proportions of lact albumen to casein have not been definitely 
agreed upon, but it exists in far greater proportions relative to the 
casein than in cow’s milk. According to Koenig, the relative propor- 
tions are as 5 to 4. The total amount of proteids varies normally 
from 1 to 2 per cent and abnormally from 0.07 to 4.5 per cent. They 
are highest during the first few days of lactation ; after the first few 
weeks they vary but little until toward its end, when they experience 
a decided decrease. 
Fat . — Fat is present in woman's milk in the form of minute glob- 
ules, and in perfect emulsion by virtue of the albuminous fluid in 
which the} 7 are suspended. It exists mainly in the form of the neu- 
tral fats, olein, palmitin. and stearin, and but small quantities of 
the fatty acids are present. Forty-three analyses by Leeds show vari- 
ations in the fat content of woman’s milk of between 2.11 and 6.89 
per cent, with an average of 4 per cent. The percentage of fat pres- 
ent in woman's milk is but little affected by the period of lactation. 
Sugar . — Sugar is the most constant of the ingredients of human 
milk in its percentage. It is present as lactose in complete solution 
in the proportions of from 6 to 7 per cent. Its quantity is least in 
the first week. After the first month its variations are very slight. 
Salts . — Only one-fourth as much inorganic salts is present in 
woman’s milk as in cow's milk, and, with the exception of the cal- 
cium in combination with the casein, are all in solution. They are 
present in the proportion of 20 per cent. 
CLINICAL EXAMINATION OF WOMAN’S MILK. 
It is often of importance to recognize the occurrence of quantita- 
tive and qualitative departures from the normal composition of 
woman’s milk occurring during lactation, and their nature, as upon 
24907— Bull. 41— OS- 
41 
