30 BACTERIA AND SOIL FERTILITY 



Some of the disease-producing organisms are found m the 

 mouth (sometimes in individuals apparently healthy) and they 

 can safely make the journey from the lips of one to the lips of 

 another on the common drinking cups. The fingers are continu- 

 ally finding their way to the mouth, and if the saliva v^ere indigo 

 what a blue world it would be! For we find that "the cook 

 spreads his saliva on the muffins and rolls; the waitress infects the 

 glasses and spoons; the moistened fingers of the peddler arrange 



his fruit; the thumb 

 of the milkman is 

 in his measure; the 

 reader moistens the 

 pages of his book, 

 the conductor his 

 transfer tickets, the 

 'lady' the fingers of 

 her glove. Every- 

 one is busily en- 

 gaged in this distri- 

 bution of saliva, so 

 that the end of each 

 day finds this secre- 

 tion freely distrib- 

 uted on the doors, 



Fig. 14. — Bacteria with flagella at both poles 

 (after Harrison). 



window sills, furniture and playthings in the home, the straps of 

 trolley cars, the rails, counter and desks of shops, and public build- 

 ings, and indeed upon everything that the hands of man touch." 

 In many cases it is the germs of disease which are sown, and if the 

 next comer has not learned that the hands are to be kept from the 

 mouth he may easily transfer them to his mouth, and if perchance 

 they find suitable soil the individual soon finds himself suffering 

 with a disease. It may be a mild attack of la grippe or a fatal 

 attack of tuberculosis. It is often the case in the home or the 

 hotel that the organisms are transferred from one dish to another 

 by the common dishcloth or dish towel. 



Cell Structure. — Many bacterial cells are surrounded by a 



