706 
The sugar of cow’s milk is practically identical with that of 
woman’s milk, and is present in the proportion of about 4.50 per 
cent. 
Salts . — Inorganic salts are present in the proportion of 0.75 per 
cent, of which calcium and phosphoric acid are the most abundant 
constituents. 
Bacteria. — Cow’s milk always contains a large number of bacteria, 
their number increasing with the age of the milk and the conditions 
under which it is kept. 
Cream -. — Cream is merely cow’s milk rich in fat to excess. It is 
obtained either by skimming the milk (gravity cream) or is separated 
from it centrifugally by a machine known as a separator. It differs 
from milk but slightly in its other solids. Very rich cream (40 per 
cent) contains relatively less sugar and proteid (sugar 3 per cent, 
proteid 2.20 per cent). The usual strengths of separated ■ creams 
marketed contain respectively 8 per cent, 12 per cent, 16 per cent, 20 
per cent, and 40 per cent of fat. 
PART III.— INFANT FEEDING. 
NUTRITIVE REQUIREMENTS OF INFANTS. 
It is obvious that any inquiry into the methods of infant feeding 
demands an intelligent comprehension of their nutritive requirements. 
Yet this phase of the question has been the object of scientific study 
only of recent years. Why this has been so, it is difficult to under- 
stand, seeing that we have long been possessed of very precise data 
as to the calorific value of the various articles composing the adult's 
dietary and the amount of heat units required to maintain their 
nutrition under various circumstances. And yet, until the investi- 
gations of Heubner and his co-workers, our knowledge of the nutri- 
tive needs of infants has been mainly empirical and based merely on 
clinical observations, observations which I may add have been the 
source of serious error. 
The world is indebted to O. Heubner of Berlin, who was the first 
of a series of investigators, now rapidly increasing, for the discovery 
of facts which go a long way toward solving the difficult problem of 
infant feeding. Heubner,® appreciating that the principles underly- 
ing the feeding of infants, could only be worked out, as in the case of 
adults, from the logical basis of the number of calories per kilogram 
of body weight required by them for the purposes of growth and 
nutrition, undertook a series of exhaustive experiments with this end 
in view. 
a O. Heubner, Die Energiebilanz des, Sauglings. Zeitschrift f . diatet. u. physik. 
Therapie, 1901, Yol. V, p. 13. 
