178 ORGANISED FLUIDS. 



MODIFICATIONS EXPERIENCED BY MILK ABANDONED TO 

 ITSELF, AND IN WHICH PUTREFACTION HAS COM- 

 MENCED. 



The first change which the milk undergoes subsequent to 

 its abstraction from the system is that which has already 

 been referred to, and which consists in the separation of the 

 globular or buttery element of the milk from its other con- 

 stituents, and its ascension to the surface of the fluid, where 

 it. forms the layer of cream ; this change in the arrangement 

 of the components of the milk is determined by the lighter 

 specific gravity of the proper milk or butter globules. 



All the milk globules do not, however, ascend and join 

 those which constitute the cream : it is chiefly the larger ones 

 which do so, the smaller remaining diffused through the sub- 

 jacent milk, to which they impart the degree of opacity which 

 belongs to it. 



These smaller globules are not, however, equally scattered 

 through the skimmed milk, the greater portion of them being 

 spread through the upper stratum of it, and the lower ap- 

 pearing almost clear and transparent, containing but few 

 butter globules, and these the smallest, as well as the minute 

 cheese globules already described. 



These changes consist merely in a different disposition of 

 the normal constituents of milk, and are unaccompanied by 

 any alteration in the constitution of its elements. The next 

 series of alterations have reference to the decomposition of 

 the milk, and are attended by changes in the actual state and 

 composition of the milk. 



The first change experienced by the milk indicative of 

 commencing decomposition is that from an alkaline to an 

 acid condition. This acidity, slight at first, goes on in- 

 creasing until at length other alterations are produced ; thus, 

 the layer of cream becomes thicker and thicker, condenses 

 itself into a mass, and finally presents almost the appearance 

 of butter; at the same time the cheese is coagulated and 

 precipitates itself to the bottom of the liquid : a portion of it, 



