ANIMAL MATTER IN MILK 33 
milk channels. They are cut across. The walls 
appear as white fibers. On the inside edge of 
the walls are numerous round balls, some white 
Courtesy M. P. Ravenel. 
SECTION ACROSS COW’S UDDER 
and some black. These are the cells forming 
the velvet lining of the milk tubes. The white 
ones contain butter fat, and the black ones are 
