DISINFECTANTS, ANTISEPTICS AND DEODORANTS 691 



been discarded by most liealth authorities both here and 

 abroad. It certainly will not kill the spores of anthrax and 

 tuberculosis, and should never be allowed to replace 

 thorough mechanical cleansing and disinfection with other 

 chemical agents, but may be utilized as an additional 

 safeguard. Chlorine gas is more reliable. Formaldehyde 

 is now being employed by many boards of health for general 

 disinfectant purposes, and it appears to be the best means 

 of gaseous disinfection. (See p. 320.) 



ANTISEPTICS. 



It is perhaps well to consider here the sources of 

 infection and the natural defenses or immunity possessed 

 by animals against parasitic invasion. Pathogenic micro- 

 organisms are commonly brought in contact with the body 

 through the agency of the air, drinking water and food, and 

 insects (flies and mosquitoes), and gain entrance by means 

 of the air passages and digestive canal ; but even now the 

 micro-organisms are in a certain sense outside of the body, 

 since it is not easy for them to penetrate the intact and 

 healthy ciliated mucous membrane of the respiratory tract. 

 But when the mucous membrane is damaged by inflamma- 

 tion, and the ciliae becomes paralyzed, and abnormal secre- 

 tions are formed, then a favorable opportunity is offered for 

 their growth and entrance into the circulation. In the 

 digestive tract the hydrochloric acid of the gastric juice and 

 bile act as natural antiseptics, while the liver is thought 

 to destroy toxins resulting from bacterial life. 



When digestion is in a normal condition, putrefaction 

 and fermentation do not occur ; but when its activity is 

 diminished, and the secretion of the digestive juices is 

 lessened, and the hepatic functions are depressed, then a 

 chance is offered for bacterial growth, fermentation and 

 absorption of toxins, or even actual transmigration of 

 micro-organisms through the intestinal walls. To these 

 natural agencies of defense, which may be likened to out- 

 lying pickets shielding the animal from bacterial invasion, 



