28 REporRT OF THE BACTERIOLOGIST OF THE 
INTRODUCTION. 
Among other subjects discussed in Bulletin No. 188 of this 
Station was the trouble known as “rusty spot in cheddar cheese.” 
The trouble has continued to appear in factories in different 
parts of the State. During the past two seasons we have studied 
it in four infected factories. Our object in this study has been 
to develop a method of control which can be applied by the fac- 
toryman with ease and certainty. This bulletin gives the results 
of our work and observations in these factories, together with the 
methods which we have devised for the control of the trouble. 
ACKNOWLEDGMENT. 
For obvious reasons the names of the factories and their makers 
will not appear in this publication but we wish to acknowledge 
our indebtedness to the factorymen for their active and intelli- 
gent cooperation during the progress of this investigation. Much 
of the success of the investigation is due to their thoughtful 
observations. 
GENERAL NOTES ON RUSTY SPOT. 
APPEARANCE IN CHEESE. 
Usually the first intimation of trouble which the factoryman 
has is the statement from the buyer that part of his last shipment 
was cut or rejected because there were spots of a reddish color 
on the inside of the cheese. Plugs drawn from cheese on the 
shelves look as though they had been lightly sprayed with red 
ink or cheese-color, depending upon whether the spots are bright 
red or vellowish red like fresh iron rust. -When a cheese is cut 
or broken open and the surface closely examined, the color will 
be found scattered in points the size of a pin point and larger. 
While this color occurs fairly evenly throughout the cheese it is 
usually most noticeable on the surface of the gas holes and other 
openings. If there is free moisture in these places the color will 
be mechanically distributed over the surface of these holes and 
form a yellowish red blotch which may be as large as the thumb 
nail. These blotches can be readily seen at a distance of several 
feet and they are responsible for the financial loss because they 
