50 RePoRT OF THH BACTERIOLOGIST OF THE 
are caught and held in the coagulum. It was to be expected 
that many of these would be liberated by the cutting and farther 
manipulation of the curd, but this does not seem to have oe- 
curred to any considerable extent in the above experimental 
cheeses. 
It should be stated that to avoid contaminating our curd mill 
the cheese was all handled as stirred curd. It is generally 
agreed that this trouble is worse in home trade than in the more 
acid export cheese, and in all these tests the attempt was made to 
produce a low-acid cheese. | 
The differences in results with cultures can not be well attrib- 
uted to differences in the cultures themselves, Since in one case 
approximately equal quantities of the same organism were used 
in two cheeses made with an interval of about twenty days. In 
the first instance the culture was added directly to the milk 
before setting with rennet, while in the other cheese the culture 
was added immediately after cutting the curd. The first cheese 
gave only very faint evidence of discoloration, while the second 
was intensely colored by a multitude of closely set yellowish-red 
points, 
CONCLUSION. 
While we are not yet in a position to give the clear-cut infor- 
mation desired by the factorymen, still the following points may 
be of assistance: , 
The rusty spots in Cheddar are simply the growth of minute 
plants on the walls of the air spaces within the cheese. While 
the growth does not seem to be harmful to the consumer, it is 
objectionable because it is unsightly. 
Coloring the cheese will cover up these spots, except in very 
bad cases. 
High acid content, with the consequently small amount of 
moisture in the air spaces within the cheese, tends to keep down 
the production of color. : 
The trouble usually appears in May, often does little harm 
through the middle of the summer, and ordinarily disappears in 
October. 
