242 MILK I ITS ORIGIN AND COMPOSITION 



very small amount only in normal milk. Dextrose as 

 well as milk sugar is present. It curdles very slowly 

 with acids and rennet : the change from the manufacture 

 of colostrum to the formation of ordinary milk by the 

 udder takes place gradually, but colostrum corpuscles do 

 not disappear entirely for two or three weeks. The milk, 

 although not unwholesome, is not generally used for dairy 

 purposes until the lapse of three to five days after 

 parturition, since cream containing it does not make good 

 butter or cheese, and the milk cannot be so readily 

 " separated." Before lactation the alveoli are found to 

 consist of solid masses of cells, between which there are 

 no alveolar cavities. Later the central cells of the 

 alveoli with their nuclei and other contents are discharged, 

 and according to some authorities become " colostrum 

 corpuscles " alveolar cavities at the same time being 

 established ; others consider that the " colostrum 

 corpuscles" are simply leucocytes which have absorbed 

 fat as an amoeba absorbs its food. 



Ex. 119, Obtain some fresh colostrum : place a drop of it 

 on a slide and cover with a clean slip. 



Examine with a f in., J in., and ^ in. objective. Note the 

 form and make drawings of the fat globules and colostrum 

 corpuscles. 



Spread a drop of colostrum on a cover-slip and allow it to dry : 

 pass through flame and dip it in ether for three minutes and 

 then in absolute alcohol for one minute, by means of which 

 treatment the fat is removed from the film : dry and stain 

 with Loffler's methylene blue, after which examine with J and 

 ^2 in. objective. 



Make drawings of bacteria and other objects which have become 

 stained a blue colour. 



4. The Enzymes of Milk. In 1897 Babcock and 



