76 MILK 



characteristic of nucleic acid and that Basch's theory could not 

 hold. 



It is difficult to form an opinion of the correctness or fallacious- 

 ness of either of these hypotheses. The difficulties that are met 

 with in investigations of this character are obvious, and for the 

 present it is necessary to confess ignorance. The same difficulty 

 holds in regard to knowing with certainty the origin of lactalbumin 

 and lactoglobulins. 



Milk-fat. — It was formerly believed that milk-fat was the 

 result of fatty degeneration of proteins, and that upon standing 

 the quantity of milk-fat would increase at the expense of casein, 

 but many observations have shown clearly that the composition 

 of milk-fat is influenced by the fat in food. This fact has led to 

 the belief that fat from food passes directly into the milk. How- 

 ever, this is not a necessary conclusion, because fat may be 

 assimilated as body fat and then reach the milk glands as such, 

 or it may be broken down into building stones and then synthe- 

 sized by the milk glands into milk-fat. In either case the result- 

 ing milk-fat would be dependent, in a measure at least, upon the 

 original fat taken from the food and would have a similar composi- 

 tion. That such is the case is shown by comparison of the iodin 

 number of body fat, colostrum fat — which is formed during a 

 transition period^and genuine milk-fat. The following table 

 given by Engel, and taken from Sommerfeld's Handbuch, illus- 

 trates the point: 



■ lodin number of ^ 



Mammal. Body fat. Milk-fat. Colostrum fat. 



Cow 42.0 32.0 46.1to50.5 



Goat 44.1 37.0 46 9 



Sheep 45.0 39.0 46 8 



Human 61.5 43.0 62.0 



Dog 72.7 58.3 



Ass 78.2 72.0 



This table shows that while there is some difference between 

 the iodin numbers of body fat and colostrum, which might be 

 expected, there is a much greater difference between body fat and 

 milk-fat. If the theory is correct that colostrum is a transition 

 product between body fluids and milk, it would follow naturally 

 that the fat of colostrum would also be a transition product. 

 Extensive investigations by Engel (quoted from Pfaundler in 

 Sommerfeld's Handbuch) have led to the conclusion that milk-fat 

 is not identical with body fat, but that, since the iodin numbers 

 of milk-fat and body fat are approximately proportionate, there 

 must be a dominating influence of body fat upon milk-fat. Milk- 

 fat therefore is dependent upon body fat, but is not identical with 

 it. Consequently, body fat is either not the exclusive source of 

 milk-fat, or the milk glands transform the body fat into milk-fat. 



