402 
Micro-organisms and their Action on Milk, 8^c. 
There are other cheeses which we are wont to see infested 
with particular kinds of mould, though as a covering on the 
outside only. We expect to see white mould on one, red on 
another, and grey on a third kind of cheese. With some 
cheeses the growth of mould changes during the process of 
ripening, as clearly indicated by distinct changes of colour. 
The manufacturer judges by the successive appearance of dif- 
ferent moulds the regular progress of the ripening process, and 
the stage the cheese is in. Whether these moulds, appearing 
on the outside of cheeses, have any influence on the ripening, 
or whether they are only a kind of indicator that the cheese has 
reached a certain stage, and is of normal quality, is a question 
which we have never heard raised. We are, however, of 
opinion that the quality of the cheese is little if at all affected 
by the outside fungoid growths, and that the latter have no 
importance beyond showing that certain changes must have 
taken place in the cheese, as they will appear only under 
certain conditions. A certain action on the cheese cannot 
be denied, such as saponifying fat, forming ammonia salts of 
the fatty acids, and liberating glycerine ; but action of this kind 
will scarcely affect more than the rind of the cheese. 
Greatly desired as are certain fungoid growths on some cheeses, 
others are as much dreaded and despised. A micro-organism, 
for instance, resembling yeast in its shape and development, 
infesting certain kinds of cheese, and producing more and more 
spreading spots of deep black colour, reduces the value of the 
cheese to a great extent, if it does not make it altogetlier unsale- 
able, on account of its affecting the taste. 
Conclusion. 
In these days science progresses at such a pace that it is utterly 
impossible for the majority of men to follow its rapid advances 
step by step. One must make a halt every now and again to 
look back at and sum up what has been done in a special i)ranch 
during a limited period which has passed. In the preceding 
pages the endeavour has been to give such a review with regard 
to the limited field indicated by the title of this article. The 
writer has felt the great difficulty of being brief, and at the same 
time clear, on subjects which can scarcely be regarded as 
generally familiar, the more so as these subjects are up to the 
present very insufficiently investigated. It should be kept in 
mind, that what was thought correct and true yesterday may be 
found to be false to day ; and what stand as isolated facts to-day 
may form part of an established system to-morrow. 
