on Milk and Milk-Products. 
399 
versally recognised, and among themselves clearly distinguished 
character, and if we take it for granted, as we have good reason 
to do, that their characteristic qualities, especially with regard 
to flavour, are the consequences of the action of different kinds 
of micro-organisms, the number of these micro-organisms would 
be by no means small. 
The question then arises, are all these micro-organisms 
present everywhere, so that the manufacture of a special kind 
of cheese, with all its characteristic qualities, is possible at any 
place, provided the conditions favourable to the development 
of the micro-organism peculiar to the cheese in question are 
well understood ? This question has been negatived, not only 
by abstract theory, but by practical experience. It has been 
contended, that with due skill and knowledge cheeses similar 
in many respects to Stilton, Camembert, Neufchatel, and the 
like, can be made anywhere, but that they will be imitations 
only, distinguished from the genuine article in some particular 
point of flavour, as long as they are made outside the district 
in which the manufacture has been carried on for ages as a 
specialty. 
The explanation given is this : in a district in which a 
certain kind of cheese, requiring for its production the action of 
a special kind of micro-organism, has been carried on for a 
great number of years, it is to be expected that such micro- 
organisms will be present in abundance, while in other districts 
they may be very rare, or even entirely absent. The success in 
making a foreign cheese would depend then not only on the 
introduction of the peculiar mode of operation, but also upon 
the importation of a particular kind of ferment or ferments. It 
is obvious that with different kinds of cheese wide differences 
must exist in this respect. While it may be an easy matter to 
make a particular kind of cheese at any place because it only 
requires ferments, which are widely spread and met with any- 
where, it may be a matter of impossibility in some localities to 
produce the cheeses whose characteristic qualities are caused by 
rare organisms. The products of fermentation had long been 
known before anything was discovered about the cause. To bring 
the causes of fermentation home to micro-organisms was a great 
step accomplished, after many difficulties had been overcome ; 
but far more difficult is it to identify the undoubtedly vast 
number of the special kinds of micro-organisms, and recognise 
the fermentative decompositions which each particular kind is 
able to produce in different kinds of media. 
In the case of cheese, research is surrounded with unusual 
difficulties. The chemical constitution of the nitrogenous matter 
forming the chief component part of cheese is not yet known, 
nor are all the bodies formed from its decomposition under 
