For infants the only satisfactory food is that of a healthy mother.  On account of physical defects in the mother, or often for merely selfish reasons, the infant is deprived of its natural food.  Many attempts have been made to bring cow’s milk to approximately the same composition as human milk.  It can be done by adding water, milk sugar and cream of known composition, in certain proportions.  Great difficulties are met with when this is put into practice.  The simplest method is that of Professor Soxhlet.  The proper quantity of milk sugar is added, but instead of adding the right quantity of cream or fat—­a very difficult thing to do—­the equivalent quantity of extra milk sugar is used.  Although not theoretically satisfactory, in practice it answers very well.  We have found it to agree very well with infants.  To cow’s milk of pure average quality, add half its volume of water containing 12.3 per cent. of milk sugar; or, what amounts to the same thing, to a pint of cow’s milk add one and a quarter ounce of milk sugar and half-a-pint of water.  It is preferable to Pasteurise by placing the bottle of milk in a vessel of water.  This water is to be heated until the milk shows a temperature of about 75 deg.  C. or 165 deg.  F., but must not exceed 80 deg.  C. or a change in the albumen of the milk takes place which affects its digestibility.  Keep at this temperature for about ten minutes.  If not required at once, a plug of cotton wool should be placed in the neck of the bottle, and it should be kept in a cold place until required.  Professor Soxhlet does not advise the addition of lime water.  The proteids are not of the same composition as in human milk (the calf being a ruminating animal)—­and it is a common plan to add water or barley water to milk until it is so watered down that it cannot curdle into tough curds.  An infant has thus either to distend its stomach with a large quantity of watery nourishment, or else to get insufficient food.  Sometimes it is necessary to peptonise the milk a little.  At the Leipzig infants hospital, and also the Hygienic Institute, they give to infants, up to 9 months old, Prof.  Soxhlet’s mixture, except that an equal volume of water is added to the milk.  Milk, cheese, and especially hen’s eggs contain a very large proportion of proteid.  When added to food poor in proteid they improve its nutritive quality.  It has often been said, and with truth, that some vegetarians by the profuse use of animal products, consume as much, or even more proteid of animal origin than the average person who includes flesh food in his dietary.  An excess of proteid from these sources is less injurious as eggs contain no purins, and milk but a very small quantity.  In support of the use of animal products, it may be said that we have become so fond of animal foods and stimulating drinks, that the use of milk, butter, cheese and eggs renders the transition to a dietary derived from the vegetable kingdom much easier.  By means of these, cooked dishes can be produced which approach and sometimes can scarcely be distinguished from those of cooked flesh.