PRESIDENT S ADDRESS — SECTION I. 24:3 



"by exposing the articles to a fine spray of suspended bacteria, the arti- 

 ficial analogy of the natural cough or sneeze. By soaking up the sus- 

 pension the articles become thoroughly impregnated, and we have a 

 condition similar to the soaking up of sputum, urine, or other infectious 

 fluid matter. The absorption of the larger spray droplets thrown out 

 in coughing will be intermediate between the two conditions. 



It may be taken as a rule that the thinner the layer of infectious 

 matter the sooner will the bacteria be destroyed. When bacterial sus- 

 pensions are sprayed upon silk threads, the microbes die much more 

 quickly than when they are soaked up and the threads carefully dried. 

 Thus Bac. prodigiosus succumbs in eight days when sprayed, and in 72 

 when soaked up ; Bad. typhi in 30 hours when sprayed, and in five 

 w^eeks when soaked up. Bacteria perish more quickly when absorbed 

 in linen than in silk, and much more speedily when in paper. Much, 

 therefore, depends upon the method by which the material has been 

 infected — whether by coughing, or sneezing, or by sputum, &c., and 

 also upon the nature of the absorbent material. By " nature " one 

 includes the kind of material — such as silk, or linen, as well as the 

 texture. The influence of the latter is well illustrated by an experiment 

 which showed that cholera vibrios perished in one hour when soaked 

 up in silk cocoon fibres and in 120 hours when absorbed by silk threads 

 one-twentieth of an inch in diameter. (8) Dust appears to be a most 

 ■effective material for bringing about a rapid destruction of bacteria. 

 In these experiments the micro-organisms were suspended in water or 

 dilute solutions of salts. In other fluids — with the exception of urine 

 — they have a longer span of life (8). The fluid in which they are con- 

 tained is of considerable importance, for they are rarely found in water, 

 the usual infectious materials being more often saliva, bronchial mucus, 

 blood, or exudates, all of which are mucinous or albuminous, and are 

 ■certain to prolong the lives of the bacteria beyond the times that have 

 heen quoted. 



An investigation relating to this part of the subject was recently 

 made by Heim.(16) Various pathogenic bacteria, contained in pus, 

 "blood, serum, &c., were found to be still alive and virulent after periods 

 ranging from three months to two years, the majority of the non- 

 sporulating microbes living for more than a year. But as in these 

 experiments the infected silk threads were dried over calcium chloride, 

 it is evident that one of the conditions was too severe to enable the 

 results to be compared with what might happen under ordinary circum- 

 stances. The thorough desiccation preserved the lives of the microbes ; 

 they would never reach such a state under natural conditions. 



The duration of life of a resting bacterium depends so much upon 

 the kind of bacterium, upon the medium in which they are, upon the 

 substratum upon or in which they rest, upon the conditions of light, 

 temperature, and moisture, that one can only say that they will be 

 ■alive after 24 hours, and may die sooner or later afterwards. We 

 have a long persistence in Heim's experiments, and as a contrast 

 Kirstein (8) found that Bac. prodigiosus when sprayed in dust, dis- 

 appeared in from six to nine hours in diffused daylight. 



