184 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
lower part of this space and discharges at the top. The 
milk is poured into a reservoir or tank at the top of 
the corrugated metallic sheets and, passing out through 
perforations in the bottom of the reservoir, flows slowly 
downward in a thin layer over the corrugated surfaces 
to a trough at the bottom, from which it passes into the 
INLET 
Fia. 19.—Corrugated type of cooler. 
collecting can or bottling apparatus. A late model of 
the corrugated type of cooler is conical in form and is 
provided with a metal cover to protect the milk from 
contamination while it is passing over the cooling sur- 
face. 
(c) The tubular cooler (Fig. 20) consists of a num- 
ber of pipes arranged horizontally, one under the other 
