136 UNIVERSITY OF WISCONSIN STUDIES 
interpretation of a large proportion of yeasts and a small 
proportion of Oidia and vice versa. Only the sum total has 
a meaning. The yeasty are more persistent. To simplify 
the language for laymen we call Oidium lactis ‘‘mold’’. 
On the basis of the record made by a number of good plants 
we have adopted an arbitrary commercial standard of ten or 
less. This is as good work as the best men are able to do. 
A count of thirty or more means one or more of the following 
defects: Failure of pasteurization, i. e., in temperature, in 
time, or by contamination; lack of cleanliness or of sterility of 
utensils and conduits; or contaminated starter. In every case 
where we made a personal survey where the count exceeded 30 
we demonstrated that one of these defects existed to such 
a degree that the laymen could easily see it when it was 
pointed out to them. By mail and without making personal 
trips we have corrected many defects. That we detected dirty 
eream pipes 500 miles beyond our eyesight and caused them 
to be cleaned is one of the wonders of our uninitiated. 
When testing pasteurization or when searching for defects, 
we present a survey of the plant by means of the graphic re- 
‘port shown here (sce Fig. 3). This maps out the course 
of the material through the plant and shows where defects 
occur. In the case exhibited here yeasts and molds in the 
pasteurized products made their first appearance in the churn, 
thereby proving it to be the source of contamination. If the 
cream were the original source of yeasts and molds, then the 
butter would contain much fewer than the cream because the 
drainage of the buttermilk aud washing of the butter eliminate 
the larger part of them. But since the churn was the source 
of the yeasts, their number increased the longer the materials 
remained in the churn. The working of the butter expelled 
more yeasts than the churning because the fixtures of the 
worker are the main refuge of yeasts. These churns were 
old and difficult to sterilize. Nevertheless this exhibit is ex- 
cellent work and far above the average. 
Other conditions being favorable, a butter having only a 
few yeasts and molds is a safer hazard for long distance ship- 
ments and for storage. Indeed, our records show that the 
