82 STORRS AGRICULTURAL EXPERIMENT STATION. 
appearance, texture or color of the medium used, or by the 
production of flavors. ‘The results may be anticipated here by 
noting that these two classes of data did not prove mutually 
interdependent, but that chemical analysis may show in general 
the chemical conditions found in a ripe cheese without the 
necessary texture and flavor and conversely the practically 
necessary texture and flavor may be obtained in a cheese differ- 
ing considerably in its chemical condition from the standard 
market article. In our practical experiments we sought first 
for proper appearance, texture and flavor of the cheeses, then 
without disturbing these, endeavored so to control chemical 
changes of the casein as to satisfy the standard of chemical 
composition established from the study of market cheeses. 
I. RELATION OF MOLDS TO ACIDITY. 
The development of lactic acid has been shown to be of pri- 
mary importance in the control of deleterious bacteria. In our 
previous paper it has also been seen that after doing its work 
this acidity gradually disappears in the ripening process. The 
disappearance of the acid has been attributed by Roger (Rev. 
Hebd. 7 pp. 334) and by Epstein (Archiv. f. Hyg. XLV. pp. 
373) and by Mazé to the activity of molds and interpreted as 
preparing the way for the action of peptonizing bacteria. This 
view of the relation of molds to cheese ripening has been widely 
quoted as their only function in the process. 
The acid exerts practically no selective action upon any of 
the molds studied. Stoll has recently shown that species of © 
Penicillium grow readily in media containing much higher per- 
centage of acid than ever occurs in cheese work. ‘The use of 
acid in fungous cultures to restrain bacteria is practically uni- 
versal. But the action of the different species of mold upon 
the acid is very different. ‘This is strikingly shown by the 
introduction of a solution of litmus into the culture media used. 
Litmus gelatine or litmus agar may be a deep blue if used at 15 
acid on Fuller’s scale as is usual for bacterial studies, or a clear 
bright red if two to four drops of normal lactic or other acid 
are added to 10 cubic centimeters of medium. No mold culti- 
vated in this work has failed to show some definite relation to 
acidity indicated by litmus reaction. Some fungi as soon 
as they develop visible colonies begin to change red (acid) 

