American Milk-Condensintf Factories. 
109 
their growth and multiplication soon convert the milk into a 
filthy, putrefactive mass, similar to that of the substance from 
which they emanated. 
"The Micrococcus, for instance," says Professor Caldwell, 
"appears only in substances rich in nitrogen, but when it does 
appear, no matter from what fungus it may come, it causes 
putrefaction ; the Cryptococcus not only causes the particular 
kind of decomposition called alcoholic fermentation, but appears 
only in solutions that are fit for that kind of decomposition, and 
so on." 
The wonderful rapidity with which these fungi produce new 
cells, each of which can act as a starting-point for new and dis- 
tinct growth, also increases their power of making their influence 
for good or evil to be felt everywhere. 
" The Penicillium crustaceum can run through its whole course 
in 48 hours at the most, at a temperature of 50° to 60° Fahren- 
heit, and produce a new crop of several hundred spores for each 
old one; and in 48 hours more each spore of this crop of several 
hundred will produce several hundred more, and so on. At such 
a rate of multiplication, it would take but a few days to reach 
numbers too great for an adequate conception. And what is 
more, this is not the only way, nor even the most rapid way, 
in which the Penicillium can propagate itself; a Penicillium 
spore will in the course of an hour, at a moderately elevated 
temperature, produce from 20 to 100 Micrococcus cells; each 
one of these cells will subdivide into two in another hour, and 
so on. At this rate of increase, we should have, at a low esti- 
1 mate, of 50 cells from one spore, to start with, four hundred 
million Micrococcus cells from this one spore in 24 hours." 
Again he says, " From the moment the milk leaves the cow 
the work of the fungi commences ; they begin to increase, and 
simultaneously the milk begins to change — both operations 
going on with a rapidity that varies according to the circum- 
stances of temperature and exposure, and never ceasing entirely 
till the milk or its products are digested in the stomach, or have 
putrefied or decayed in the air, producing results that vary 
according to the product, whether butter or cheese, or simply the 
milk itself; and what is very important and more pertinent to 
my subject, according to the kind of fungus that gets a foothold 
i in the substance. The elements of fungi that are already in pure 
! clean milk, to begin with, or that are added in the rennet (when 
! cheese is made), appear to do no harm ; but, on the contrary, by 
their legitimate growth and action on the substance in the midst 
of which they find themselves, to bear at least an important part 
in the elaboration of the very principles which give the final 
product its savour and its value. But the case is quite different 
