Am.  Jour.  Pharm.  1  Books  dS  d  Source  Off  Disease.  IQ 
sunlight,  which  is  a  great  factor  in  keeping  the  germs  in  an  inactive 
state.  '  j 
But,  besides  the  danger  of  infection  from  inhaling  disease  germs 
found  in  the  dust,  there  is  also  to  be  considered  that  it  is  the  cutting 
edges  of  the  particles  of  dust,  which  when  inhaled  scratch  or  cut  the 
delicate  air  passages  leading  to  the  lungs  and  also  the  lungs  them- 
selves. The  finer  dust  will  not,  perhaps,  act  as  quickly  as  the  coarser 
grains,  but  it  means  that  the  evil  result  will  take  a  much  longer  time 
before  making  its  appearance. 
It  is  known  that  those  who  spend  most  of  their  time  in  outdoor 
occupations,  generally  have  better  health  than  those  who  are  com- 
pelled to  work  in  factories,  offices,  etc.,  and  the  first  thought  of  sani- 
tary science  to-day  is  the  elimination  of  dust. 
It  is  extremely  difficult,  in  fact  almost  impossible,  to  trace  many 
cases  of  infection  on  account  of  the  long  period  between  the  first 
infection  and  the  appearance  of  the  disease  in  a  form  to  demand 
medical  attention. 
Dr.  Hugh  H.  Brown,  of  Washington,  D.  C,  and  an  assistant,  in 
1907,  moved  a  large  number  of  books  which  had  not  been  disturbed 
for  quite  some  time.  Within  a  few  days  both  contracted  severe  colds, 
characterized  by  distinct  bubbling,  and  a  severe  cough  accompanied 
by  a  feeling  of  compression  and  pain  in  the  chest,  and  an  exceed- 
ingly profuse  and  purulent  expectoration  of  a  deep  yellow  color  the 
consistency  of  thick  cream.   The  cold  lasted  about  two  weeks. 
Vitality  of  Bacteria. — Before  considering  the  mode  of  overcom- 
ing these  organisms,  consideration  should  first  be  given  to  their 
power  of  resistance  to  disinfection,  sterilization,  etc. 
Bacteria  exist  in  nature  in  three  states : 
( 1)  As  adult  or  fully-developed  and  active  microorganisms,  with 
all  the  characteristics  of  parasites. 
(2)  As  spores  or  reproductive  cells  endowed  with  latent  life. 
(3)  As  desiccated  germs,  whose  vital  principle  had  been  sus- 
pended but  not  destroyed ;  which,  when  placed  in  a  moist  and  suitable 
environment,  possess  the  power  of  resuscitation. 
"  The  air  germs,"  says  Professor  Tyndall,  "  differ  much  among 
themselves  in  their  tendency  to  development ;  there  are  some  which 
are  young  and  there  are  others  which  are  old,  some  dry  and  some  wet. 
The  same  water  infected  by  those  germs  requires  more  or  less  time 
to  develop  bacterial  activity.  This  explains  the  difference  in  the 
rapidity  with  which  epidemic  diseases  act  upon  different  persons. 
