g 2 ILLINOIS STATE DAIRYMEN^ ASSOCIATION. 
proper investigation, cannot avoid them if he enters upon the sub¬ 
ject at all. The microscope shows in the solution from rennet as 
much of the germ theory of change as it does in the fermentation of 
milk when left exposed in the ordinary manner, and this evidence is 
convincing in a very high degree. Other phenomena coincide to 
make the conclusion irresistable. The living organism in the rennet 
is killed by heat, it propagates itself in a suitable liquid with the 
astonishing rapidity of its congeners usually found outside of living 
animals; a little used as seed permeates a great bulk of nutritive 
substance, as a little leaven (yeast, a plant) in the olden as well as 
the modern time, leavened the whole lump. The rennet plant can 
thus be cultivated, as the yeast plant is, and possibly in a much more 
convenient method than at present known. It is a plant, living, 
multiplying, absorbing, assimilating, dying—very low in the scale of 
classification, and scarcely differing from the equally low forms of 
animal life, yet having a definiteness and individuality which in 
some respects those of the highest rank, the lords of creation, might 
do well to imitate. 
Let this example suffice. If the coagulation of sweet milk, by 
the aid of rennet, can be proved to be due to the action of organisms 
in a living state are we not prepared to accept the same or a similar 
agency for any change which we observe in this, apparently, un¬ 
stable fluid? But the evidence concerning some of these changes, as 
that of souring, is still more direct, certainly better and more gener¬ 
ally known. We cannot be far wrong in concluding that all the pro¬ 
cesses, through which milk and its products pass, are results, dii ect 
or indirect, of living, lowly organized plants or animals. Customers 
say the higher organized animals have something to do with certain 
changes of wdiich we do not speak. 
What is the nature of the microscopic creatures to which such 
marked results are attributed ? The word fungi , now in general use, 
is commonly introduced whenever any name is applied to the organ¬ 
isms with which we have to deal. But this is applied to an immense 
order of plants of which the members differ among themselves 
almost as much as the trees of the forests and grasses of the fields. 
They have something in common as to their food and mode of life, 
but differ wondrously in appearance, in size, in method of propaga¬ 
tion, etc. There are probably not less than twenty-five hundred 
species of fungi growing naturally in Illinois. Some are found upon 
old logs, some on upright trunks, some on or in the soil, some only 
