60 



MILK 



This mixture of protoplasm and chromatin breaks up further 

 into fragments (corpuscles of Nissen). These fragments may 

 attach themselves to fat globules and then take the shape of hel- 

 mets, caps, or sickles. 



Besides organized cells, small structureless particles are fre- 

 quently observed, which are readily stained with anilin dyes. 

 These particles may form aggregations of considerable size, large 

 enough to form emboli in the alveoli (Fig. 23). Later calcium 

 and magnesium salts crystallize on these clusters and give a radi- 

 ated appearance. These bodies are clearly degeneration forms 



Mi 



Fig. 23. — Calcium salt aggregations in cow's milk, magnified 1000 (Ernst). 



and not — as has been supposed — antecedents of casein or fat. 

 Leukocytes may digest them, but they may also resist the phago- 

 cytic action and increase in size. 



The Nature of Fat Globules 

 Leewenhoeck in 1697 was the first to give a description of the 

 microscopic appearance of fat in milk. He described the globules 

 as disks, strongly refractive and without discernible structure. 

 When milk is cooled the fat congeals and globules lose their disk- 

 like shape, become irregular, and assume a wrinkled surface. 



The size of fat globules varies from less than 1 micron to 22 

 microns, and the number in one cubic centimeter of milk may be 



