8 BULLETIN 849, U. S. DEPARTMENT OF AGRICULTURE. 
From the ideal sanitary standpoint class 1 is to be preferred. Most 
dealers, however, do not consider it objectionable to pump the milk 
before pasteurization, provided the pump is of the right type and 
properly taken care of. The economy of dumping milk and leaving 
the cans on the ground floor is of considerable importance and much 
labor, time, and power may be saved by handling cans in that way 
rather than by elevating the full cans and, after dumping, sending 
them back on an elevator. Where there is not room enough on the 
ground floor for weighing, sampling, and grading it may -be con- 
venient to send the milk upstairs in cans. This system as a rule is 
more expensive, as is shown later in Table 2. 
3. Pump to higher level, then gravity—The milk is dumped into 
a tank on the first floor and pumped to a floor above, whence it flows 
through the various pieces of apparatus by gravity, without the fur- - 
ther use of a milk pump. 
Some of the most modern large plants, which vary in height from 
2 or 3 stories upward, come under class 3. It is'less objectionable to 
pump milk before pasteurization, when contamination can do less 
harm, than after. This type of plant also has the desirable feature 
of dumping and weighing the milk on the ground floor and is more 
economical in receiving milk than plants in classes 1 and 2. 
4. Pump to higher level, then gravity and pump—The milk is 
pumped from the first to a floor above. From that point it is handled 
by pumps, or partly by pumps and partly by gravity. 
Many of the larger plants belong to class 4. This type has the 
economical advantages of the plants of class 3 and in addition per- 
mits greater economies in labor by the fact that the various pieces of 
apparatus are comparatively close together, and in some cases on 
fewer floors. In most of the plants of class 4 milk is pumped after 
pasteurization and the number of milk pumps and length of milk 
piping required are usually greater than in plants of the other classes. 
Many of the plants studied in this class were comparatively old. 
5. Gravity, one story.—The milk is handled on one floor without 
milk pumps. Large quantities of milk can not be handled rapidly 
in such plants, and only the smaller plants come under this head. 
The plants of this class include a few small ones where the pasteur- 
izer was raised on a platform and the milk dumped directly into it. 
Those handling between 501 and 1,000 gallons daily were raw-milk 
plants. 
6. Pump, one story.—The milk is handled on one floor, one or more 
pumps being used. Class 6 includes some of the less up-to-date 
plants, which are usually frame buildings, built some time ago. The 
amount of milk piping required is comparatively large. Many of 
the smaller plants come under class 6; 48 out of a total of 55 handling 
less than 500 gallons each daily were in this class. A few of the 
