DISTKIBUTION AND HABITAT OF THE BACTEBIA. 719 



also in the case of cholera, where, owing to the fact that infection by 

 the linen becomes soaked with the nutrient substances 

 contained in the dejecta, multiplication of the pathogenic 

 agents may occur on it, so long as drying does not take 

 place. Infective diseases of wounds, diphtheria, puer- 

 peral fever, tuberculosis, &c., are also without doubt 

 frequently carried by linen and dressings. Unfortu- 

 nately we do not as yet know, and must still ascertain 

 by exact researches, how far the usual methods of 

 cleansing linen destroys the infective agents, or how 

 long they may retain their vitality in linen which has 

 been \vashed and put away. 



The dwelling offers many opportunities for the pre- Occurrence of 

 servation and distribution of bacteria, and especially of 

 facultative and obligatory parasites ; a multiplication 

 within the materials, which in a narrow sense belong to 

 the dwelling, does not seem to occur. The soil under the In the soil 

 floors forms, according to Emmerich's investigations, a UI 

 particularly favourable reservoir, and often contains 

 enormous numbers of saprophytic, and not uncommonly 

 also of pathogenic bacteria. These are present partly 

 in the original and for the most part very impure 

 material, and in part they reach it through the medium 

 of the water used for scouring, which carries with it 

 sputa, remains of dejecta, &c., and passes through 

 the numerous joints and seams of the floor into the 

 porous material beneath. In this way the bacteria of 

 pneumonia, spores of tubercle bacilli, &c., can readily 

 reach the soil. It is probably quite exceptionally that a 

 multiplication of bacteria occurs here, because as a rule 

 the material contains very little water. But it is pro- 

 bable that various forms of bacteria can be preserved in 

 the porous mass in a manner similar to that which 

 occurs in the natural soil. The bacteria can be ex- 

 tremely readily detached and distributed from this 

 reservoir by the mechanical disturbances to which the 

 floor of a dwelling- room is exposed ; the large masses of 

 dust which rise from the seams at every step can be 

 readily seen in a beam of sunlight. Where the flooring 

 is close and covered with oil colours, more especially, 



