220 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
Fig. 28. It was made by dividing a receiving tank of 
100 gallons capacity into four compartments of 25 gal- 
lons capacity each and providing an outlet valve and a 
cover for each compartment. Fig. 29 shows a retarder 
of the tank type. The milk from the pasteurizer enters 
at A and is carried by the pipe to the bottom of the 
first compartment. When this is filled, it overflows into 
the trough C, whence the milk flows through a 
pipe leading to the bottom of the second compartment. 
The other compartments are filled successively in the 
COVER FOR COMPART- 
SS Ee 
Fira. 28.—A simple holding tank (B. A. I. Cire. 184). 
same manner. When the last compartment overflows 
the milk enters the funnel B and passes to the cooler. 
After all the milk has come over from the pasteurizer, 
the tank is emptied by removing the funnel B and then 
taking out the plugs from each compartment succes- 
sively. 
A combined pasteurizer and holder, which may also 
be used to cool the milk, is shown in outline in Fig. 30. 
After the milk has been heated to the temperature de- 
sired and held for the required time, it can be cooled 
by replacing the hot water with cold water and then 
with ice water or brine. 
