COOLING AND AERATION 41 
bonic-acid gas. These gases should be removed as quickly 
as possible after milking by exposing the milk in thin 
sheets to the atmosphere. Fortunately the construction 
of modern coolers is such as to make it possible to do 
the cooling and aerating in one operation. 
Formerly it was customary for dairymen to aerate 
their milk before cooling. Such practice is known to give 
somewhat better aeration than is possible where the cool- 
ing and aerating are performed in the same operation; 
yet the difference is so slight that consumers cannot detect 
it. The practice of aerating first and cooling afterward 
is therefore being abandoned. 
Coolers. All modern coolers permit cooling with ice 
water. Without this a sufficiently low temperature can- 
not be obtained to stop practically all bacterial growth. 
To meet the requirements of dairies of different sizes, sev- 
eral styles of coolers are herewith described and illus- 
trated. 
Corrugated Cooler. This style of cooler is shown in 
Fig. 5, which also shows a desirable method of fastening 
it. It is especially adapted to dairies having from fifteen 
to thirty cows. The cooler consists of two parts: An 
upper section which is used to cool milk and cream with 
uniced water, and a lower section through which ice water 
is circulated. 
A storage tank for well water may be placed above 
the ceiling. From this the water is admitted to the upper 
section through the valve which is used to regulate 
the flow. As shown by the arrows the water enters the 
section at the bottom and discharges at the top. The 
waste water may be conducted to the feed water tank of 
the boiler, to a watering trough, or other places where 
it may be useful. 
