Preservation of Milk. Ill 



evidence to show that it is modified casein due to the rapid 

 evaporation of the milk serum at the surface of the milk. 



3. Digestibility. Considerable difference of opinion 

 has existed in the minds of medical men as to the relative 

 digestibility of raw and heated milks. A considerable 

 amount of experimental work has been done by making 

 artificial digestion experiments with enzyms, also diges- 

 tion experiments with animals, and in a few cases with 

 children. The results obtained by different investigators 

 are quite contradictory, although the preponderance of evi- 

 dence seems to be in favor of the view that heating does 

 impair the digestibility of milk, especially if the tempera- 

 ture attains the sterilizing point. 1 It has been observed 

 that there is a noteworthy increase in amount of rickets, 9 

 scurvy and marasmus in children where highly-heated milks 

 are employed. These objections do not obtain with refer- 

 ence to milk heated to moderate temperatures, as in pas- 

 teurization, although even this lower temperature lessens 

 slightly its digestibility. The successful use of pasteurized 

 milks in children's hospitals is evidence of its usefulness. 



4- Fermentative changes. The normal souring change in 

 milk is due to the predominance of the lactic acid bacteria, 

 but as these organisms as a class do not possess spores, 

 they are readily killed when heated above the thermal death- 

 point of the developing cell. The destruction of the lactic 

 forms leaves the spore-bearing types possessors of the field, 

 and consequently the fermentative changes in heated milk 



1 Doane and Price (Bull. 77, Md. Expt. Stat., Aug. 1901) give quite a full resumS 

 of the work on this subject in connection with rather extensive experiments 

 made by them on feeding animals with raw, pasteurized and sterilized milks. 



a Kickets is a disease in which the bones lack sufficient mineral matter to give 

 them proper firmness. Marasmus is a condition in which the ingested food seems 

 to fail to nourish the body and gradual wasting away occurs. 



