agency of bacterial life.  And so the food material of animals and plants continues in this never-ceasing circulation.  It is the sunlight that furnishes the energy for the motion.  It is the sunlight that forces the food around the circle and keeps up the endless change; and so long as, the sun continues to shine upon the earth there seems to be no reason why the process should ever cease.  It is this repeated circulation that has made the continuation of life possible for the millions and millions of years of the earth’s history.  It is this continued circulation that makes life possible still, and it is only this fact that the food is thus capable of ever circulating from animal to plant and from plant to animal that makes it possible for the living world to continue its existence.  But, ah we have seen, one half of this great circle of food change is dependent upon bacterial life.  Without the bacterial life the animal body and the animal excretion could never be brought back again within the reach of the plant; and thus, were it not for the action of these micro-organisms the food cycle would be incomplete and life could not continue indefinitely upon the surface of the earth.  At the very foundation, the continuation of the present condition of Nature and the existence of life during the past history of the world has been fundamentally based upon the ubiquitous presence of bacteria and upon their continual action in connection with both destructive and constructive processes.

Relation of bacteria to agriculture.

We have already noticed that bacteria play an important part in some of the agricultural industries, particularly in the dairy.  From the consideration of the matters just discussed, it is manifest that these organisms must have an even more intimate relation to the farmer’s occupation.  At the foundation, farming consists in the cultivation of plants and animals, and we have already seen how essential are the bacteria in the continuance of animal and plant life.  But aside from these theoretical considerations, a little study shows that in a very practical manner the farmer is ever making use of bacteria, as a rule, quite unconsciously, but none the less positively.

Sprouting of seeds.

Even in the sprouting of seeds after they are sown in the soil bacterial life has its influence.  When seeds are placed m moist soil they germinate under the influence of heat.  The rich albuminous material in the seeds furnishes excellent food, and inasmuch as bacteria abound in the soil, it is inevitable that they should grow in and feed upon the seed.  If the moisture is excessive and the heat considerable, they very frequently grow so rapidly in the seed as to destroy its life as a seedling.  The seed rots in the ground as a result.  This does not commonly occur, however, in ordinary soil.  But even here bacteria do grow in the seed, though not so abundantly