DEVELOPMENT OF PLANTS 153 



habit of spitting could be stopped. The spores and plants are 

 readily carried away in the air from the dried sputum to be 

 inhaled again and so spread the disease. The bacteria causing 

 lockjaw, or tetanus, are especially abundant in the soil in certain 

 localities. Through wounds they are carried into the system. 

 These and some other bacteria are peculiar in that they can not 

 grow in the presence of oxygen. Consequently the dangers of 

 infection are great in deep wounds. An immediate cauterization 

 of the entire surface of the wound will kill the organisms. Other 

 well known bacterial diseases are pneumonia, diphtheria, Asiatic 

 cholera, typhoid, and splenic fevers and grippe. It should be 

 noted that many diseases as smallpox, malaria, hydrophobia, 

 yellow fever and probably scarlet fever, etc., are due to a low 

 order of microscopic animal life. Disease producing bacteria 

 are either localized, as in the lungs, throat, intestines, or are 

 generally distributed throughout the system. The symptoms 

 of the disease are largely due to the products of decomposition 

 caused by the growth of the bacteria or by secretions from the 

 bacteria themselves all of which act as poisons and are commonly 

 referred to as toxins. In other cases the toxins are formed by 

 the infected animal owing to the disturbance of its growth and 

 nutrition by the bacteria in its tissues. In the same way bacteria 

 are the cause of many diseases among the plants, as in corn, 

 melons, many fruits, etc. See Bacteria in Relation to Plant 

 Disease, by Edwin F. Smith. 



These bacteria are constantly finding their way into our bodies 

 by means of the breath but so long as the system is in a healthy 

 condition there is only slight danger of the organism gaining 

 a foothold. Just how the system is able to combat the growth of 

 these plants is now the subject of earnest investigation. Certain 

 diseases, as mumps, measles, whooping-cough, smallpox, etc., 

 usually occur but once and it is probable that substances are 

 formed in the body as a result of the presence of the bacteria or 

 animal organisms that prevent a second growth of the germs and 

 the individual thus becomes immune to further attacks. The 

 formation of such a substance is known to occur in the case of 

 diphtheria. The bacteria of this disease occur in the upper air 



