CREAM. 209 



Cream is simply the butter globules of the milk 

 gathered into adherent masses (figure 52, Chapter XX.), 

 togetlier with a small quantity of the milk held by mo- 

 lecular attraction among and between the fat globules. 

 Milk consists really of a colorless liquid in which are 

 suspended an enormous number of minute globules. As 

 has been stated in the previous chapter, some erroneous 

 views have been held in regard to the character of these 

 globules wliich constitute the fatty portion of the milk, 

 and some discussion is still made by misinformed per- 

 sons in support of the now exploded theory, that these 

 globules are enclosed in a thin membrane of albuminous 

 matter. It may be interesting to readers to know by 

 what experiments the true nature of these globules may 

 be demonstrated. 



As milk is a serous viscous fluid, and adherent and 

 adhesive, when air is forced into it it forms and pro- 

 duces a cohesive froth, consisting of small and large 

 air bubbles. This is precisely the character of beer, or 

 a solution of soap, gum, syrup, or any other mucilaginous 

 or saccharine fluid. If a quantity of any of these fluids 

 is warmed to the temperature of new milk, or 100°, and a 

 small quantity of butter oil is added and thoroughly 

 mixed with it, and the mixture is agitated, the oil soon 

 separates into small globules, which, when viewed under 

 a microscope, appear in every respect precisely similar to 

 the butter globules in milk. This mixture is known as 

 an emulsion, and similar mixtures are commonly used in 

 medicine for the purpose of administering oils in a con- 

 venient and desirable form. 



When such an emulsion is permitted to remain at rest 

 tlie globules rise to the surface slowly and form a cream. 

 The appearance of these globules under, the microscope 

 gives precisely the refractive rings around them which 

 have been supposed by inexpert observers to be surround- 



