U. S. DEPARTMENT OF AGRICULTURE. 
the product would equal in quality that made in Europe, since the 
same methods were used on both sides of the Atlantic. 
The most serious trouble of the cheesemaker occurred during the 
cold months, which led to the practice of making cheaper varieties 
of cheese in the spring and fall and closing down the factory for four 
months in the winter. This, of course, is a considerable handicap to 
the industry, and would not be necessary if there were sufficient infor- 
mation concerning the origin of and remedy for the faults in manu- 
facture. These unsatisfactory conditions led to the investigations 
reported in this bulletin, since it was believed that the present faulty 
methods might be corrected, provided the real causes of cheese defects 
were discovered. 
In the absence of exact knowledge it was natural that erroneous 
theories should become prevalent in regard to the feeding of the cows, 
the care of the milk, and the handling of the cheese ; but as they were 
based on practical experience it has not been found advisable to set 
them aside without investigation. Apparently very unimportant 
changes made in handling the cheese were found to result in great 
changes in the quality of the finished product, and although changes 
in methods are necessary in order to produce the best quality of 
cheese, it is unwise to advise the cheesemaker to change his methods 
without substantial proof of the value of the change. 
The main trouble in making Swiss cheese is known to be caused by 
the development of undesirable types of microorganisms, some of 
which produce abnormal gas, causing what is known as " nissler " or 
"pressler" cheese. These undesirable organisms in Swiss cheese 
cause a lack of uniformity in the formation of the eyes. In some 
cases no eyes whatever are developed ; this trouble is probably due to 
the absence of certain desirable types. At the beginning of this work 
it was thought that these faults might be overcome by the proper use 
of starters, which have become general in buttermaking, and their 
value has been frequently demonstrated. They have also been used 
to some extent in the making of Cheddar cheese. Unconsciously the 
makers of Swiss cheese have used starters with the rennet, a practice 
which has at times been of great value. But while the rennet starter 
has been the cause of much help, it has also caused trouble when the 
helpful species of bacteria usually present have for some reason been 
weakened. The full benefit of the starter was not obtained, in any 
event, since less than one-fourth of 1 per cent of rennet was used. 
THE SIGNIFICANCE OF BACILLUS BULGARICUS IN MAKING SWISS 
CHEESE. 
In selecting a starter for making Swiss cheese it is at once apparent 
that certain characteristics are desirable to make its use possible 
with the method of manufacture employed. The curd for Swiss 
