ENTRANCE OF PATHOGENIC BACTERIA 55 



by the resulting diminished sickness and death-rate, would 

 rapidly repay any expense entailed. 



Some diseases are more or less communicated from individual 

 to individual by direct contact. The venereal diseases now 

 occupying so much attention, are almost exclusively so commu- 

 nicated, though dirty towels and dishes are by no means infre- 

 quently another method of spread ; whilst tobacco-pipes and 

 glass-blowers' tubes are also well-recognised means of their 

 carriage to innocent persons. Diphtheria and pulmonary 

 tuberculosis, influenza and common colds and many other in- 

 fective diseases may be communicated by kissing, or by breath- 

 ing the fine spray of mucus or saliva ejected by the patient on 

 coughing or sneezing. A peculiarly fatal form of plague, 

 known as plague-pneumonia, is similiarly distributed. Again, 

 some diseases, such as scarlet fever and smallpox, can be trans- 

 mitted by articles which have been in contact with the patient, 

 such as dishes, clothing, bedding, books, etc. Typhoid fever is 

 spread by bacteria in the stools, urine, and other discharges 

 which may lead to contamination of food, water-supplies, and, 

 as is well known, shell-fish which grow near sewage-effluents. 



One public health problem which is only beginning to receive 

 the attention it deserves, is what is called the " Carrier Ques- 

 tion." Many persons who have suffered from, say, typhoid 

 fever or diphtheria, continue during convalescence, and even 

 for months and in some cases many years afterwards, to harbour 

 the causal organisms of these diseases in their bodies, and act 

 as distributing centres to which many epidemics have been 

 traced. Even apparently healthy persons, who have not as far 

 as is known suffered from a definite attack of these diseases, 

 may similiarly have these organisms in their bodies and may 

 act as "carriers." Outbreaks of typhoid and of diphtheria, 

 especially in institutions such as asylums, hospitals, and schools, 

 have of late years frequently been traced to infection from 

 such "carriers." Domestic animals may act in a similar way, 

 and cases, for example, of diphtheria in the human subject have 

 been traced to infection from the domestic cat. 



In order to preserve the health of the individual, it is there- 

 fore obvious that two sets of measures must be brought into 

 play. The resisting powers must be maintained in as high a 

 state of efficiency as possible. Good housing, fresh air, light 

 and exercise and sleep, good and sufficient food and clothing, 

 are important factors from this point of view. Secondly, there 

 is the avoidance of undue exposure to infection a clean food-, 

 water-, and milk-supply, the isolation of infectious cases, and 

 the disinfection of their excreta, etc., and the destruction of dis- 



