No. 7. DEPARTMENT OF AGRICULTURE. 287 



two, and in a few minutes tliese have become full-grown, and each 

 divides again. The other is by means of spores. The contents of 

 the bacterium collects in different parts of the body, which then 

 breaks up, and each spore can, under favorable conditions, become a 

 new plant. The spores are much more resistant to heat than the 

 plants themselves, and will often remain alive for years, even under 

 the most adverse conditions. Some of them are not killed by the 

 heat of boiling water, if the temperature is not kept up too long. 

 They can also withstand great cold. Temperatures of 350 degrees 

 below zero F. have been unable to kill them. 



These, then, are the objects with which we have to deal when 

 we consider the subject of sanitation. Millions of these little plants 

 are everywhere. They flourish in the barn, in the house, in the 

 water we drink, in milk. They grow in dampness, and easily dry 

 up and are carried around by every breath of air. They flourish in- 

 side of our bodies, and are ejected with the sputum, so that the 

 sign is almost omnipresent, "Don't spit on the floor." 



It is sometimes thought that bacteria are always harmful, and 

 that the very word "germ" suggests disease, but this is by no means 

 the case. Most bacteria are beneficial; they live in organic matter 

 and return it to its natural elements. If it were not for them, or- 

 ganic matter would not decay, and how could we live with all the 

 dead trees, leaves, and animals of former ages lying on the surface 

 of the earth? Or what would our crops do for food, if vegetation 

 of previous years and centuries had not returned to its elements? 



The plants we cultivate in the fields, take the elements found in 

 the surface of the earth, and live by appropriating them. The bac- 

 teria lives by tearing apart the larger plant, and returning the ele- 

 ments to the soil where the higher plant can use them again. It is 

 this bacteria in manure which gives it part of its value; manure 

 must be handled so as to get greatest benefit from them. Thus 

 there is a perpetual cycle, 'each taking its part m the never-ceasing 

 round. 



As in the higher plant life, so among the bacteria, there are 

 harmful plants, or we might say, poisonous weeds. Some, when 

 taken into the stomach, help digest our food; others produce death, 

 perhaps by digesting us. As in the case of wild plants, the harm- 

 ful and poisonous ones receive the most attention, so the harmful 

 bacteria have been so frequently discussed tliat it has given the 

 whole class a bad name. With the beneficial bacteria we are but 

 slightly concerned. They are usually so abundant that we need 

 take no care to get them. Inoculating the soil on a new alfalfa 

 field is an exception. Here we want a new bacteria. 



For our purpose, harmful bacteria can b^^ divided into two classes: 

 those which secrete a poison, and those which miiltiply until there 

 is nothing left to live upon. An example of the first kind is thft 

 typhoid germ, which Tiroduces a poison in which it cannot live, and 

 HO if the patient will live for about six weeks, the germs will all 

 die, and the person get well. This is what is meant by "disease 

 running its course." The other kind is like the tuberculosis or con- 

 sumptive germ, which exudes no poison, but may live months or 

 years, and kills the patient by destroying the organ in which it 

 is found. 



