15 



They appear with well marked outlines, dark at the edges, and 

 bright in the centre. They are simply fat globules which are pre- 

 vented from uniting by being immersed in milk plasma, which con- 

 tains casein in a swelled state. "We distinguish three sizes of glob- 

 ules. 



1. The very large, and comparatively lightest, which, on ac- 

 count of their larger volume, rise first, and form the first cream 

 on the milk. They are said to contain the fats of lowest melting 

 points. 



2. The medium size form the main constituent of a good milk. 



3. The smallest, of which good milk contains but few, and 

 poor milk large quantities. 



White milk contains more of these butter globules than blue 

 milk. 



A normal milk should contain these globules moderately dense ; 

 they should be well-formed and separate, and should form the only 

 shaped portion of the milk. Milk of older cows is generally richer 

 in large globules. 



If the majority of the globules is small and poorly shaped, it 

 indicates that the milk is poor in fat, and lacks in nutritive 

 qualities. 



Watered and skimmed milk : The watered milk contains 

 the fat globules in the same proportion, as far as size is concerned, 

 as they are found in normal milk. The number of globules in the 

 field differs according to the quantity of water added. 



Skimmed milk generally contains none of the larger butter 

 globules, these having been removed with the cream. 



Value of microscopical examination : The value of milk 

 can never be determined by means of the microscope. Author 

 concurs here with Yieth, who says : " The microscopical exam- 

 ination of milk may, under circumstances, furnish valuable indica- 

 tions, if used for the detection of abnormal qualities in appearance 

 or behavior, or the determination of foreign substances added to 

 the milk. As a control for the determination of the fat, it has no 

 more value than other, even the best optical methods." 



Colostrum corpuscles: Colostrum corpuscles are globules of 

 from four to five times the diameter of the fat globules. They 

 consist of proto-plasma which encloses fat globules. Occasionally 

 an eccentric nucleus may be observed (see cut, page 16). 



