BACTERIA AND DISEASE 357 



all those of a spherical form, the bacilli are all oval or rod- 

 like, and the spirilla are either curved or twisted. The mode 

 of entrance of these various bacteria into the human body 

 may be by either air or by food. Bacteria, in order to produce 

 disease, must find an entrance into the tissues of the body in 

 some way. By inhalation, they would be deposited in the 

 mouth or nose, or in some other part of the respiratory truer ; 

 by food, they could gain entrance to the mouth, the stomach, 

 or the intestines. In contagious diseases, the propagation 

 would be either through breathing the atmosphere of the sick- 

 room or through personal contact, in which case the contagion 

 is probably conveyed by the hands to the mouth. 



6. Toxines and Ptomaines. As soon as the bacteria gain 

 entrance to the human body in any of the above enumerated 

 ways, and find a proper surface for their development, they 

 live upon the albumen of the tissues which they inhabit. 

 Here again, as shown in the yeast example, a rapid propaga- 

 tion takes place, and consequently a rapid spreading into 

 adjacent, and even far distant, parts of the body. Their 

 growth in the living tissues of the human body results in the 

 production of poisonous substances, called toxines and pto- 

 maines ; to these the symptoms of disease are ascribed. 



7. Antitoxine. After certain of the bacterial diseases have 

 run their course, and the patient has recovered, there seems to 

 be established in the body the power to resist future attacks, 

 as, for instance, in cases of typhoid fever, smallpox, and scar- 

 let fever. This condition is explained by the fact that the 

 bacteria of the disease have produced in the blood a new sub- 

 stance, which prevents a subsequent growth of the same kind 

 of bacteria in that person. To this new product has been 

 given the name of antitoxine, and this method of Nature's for 

 protection against disease is now utilized both in its cure and 

 in its prevention. The period during which any person who 

 has had the disease is protected from future attacks, varies in 

 different persons and in different diseases. 



6. Toxines and ptomaines, how produced* 



7. Antitoxine, its nature and effect ? 



