m'Av£*; ml™'}  United  States  Public  Health  Service.  157 
of  yellow  fever  in  the  Southern  States  in  1905.  Under  the  above- 
mentioned  laws  and  a  few  minor  ones,  there  was  finally  developed 
the  national  system  of  quarantine  as  it  exists  to-day — a  system,  the 
development  of  which  occupied  approximately  100  years. 
All  quarantine  operations  in  the  United  States  are  conducted 
under  the  supervision  of  the  Federal  Government,  and,  with  two  or 
three  exceptions,  all  stations  are  conducted  by  Federal  officers. 
A  long  series  of  immigration  laws  have  been  enacted  between 
the  periods  March  20,  1819,  and  February  20,  1907,  their  general 
objects  from  a  hygienic  standpoint  being  the  improvement  of  the 
health  and  comfort  of  arriving  aliens,  and  the  development  of  a 
stronger  race  in  the  United  States. 
On  arrival  at  domestic  ports,  all  aliens  are  required  to  undergo 
medical  inspection,  and  for  those  suffering  with  disease,  hospitals 
are  maintained.  This  medical  inspection  is  conducted  by  the  Public 
Health  Service. 
The  administrative  procedures  in  international  sanitation  having 
been  established,  and  their  further  improvement  assured,  the  great 
public  health  problems  of  the  Nation  are  now  of  an  interstate  and 
intrastate  character. 
The  Federal  public  health  statutes  are  based  upon,  or  are  care- 
fully in  accord  with  that  clause  of  the  Constitution  which  gives  the 
right  to  Congress  to  regulate  commerce  between  the  states.  On 
account  of  the  far-reaching  effect  of  interstate  intercourse  on  our 
national  life,  the  field  for  public  health  activities  on  the  part  of  the 
Federal  Government  is  wide. 
Under  the  quarantine  act  of  February  15,  1893,  the  secretary  of 
the  Treasury  is  authorized  to  issue  regulations  for  the  prevention 
of  the  spread  of  infectious  and  contagious  diseases  from  one  state 
to  another,  where  the  regulations  of  the  states  are  inadequate. 
These  regulations  may  be  enforced  by  state  and  local  authorities, 
but  the  Federal  Public  Health  Service  is  authorized  to  cooperate  in 
their  enforcement,  and  should  the  states  fail  or  refuse,  the  Presi- 
dent may  adopt  such  measures  as  in  his  judgment  shall  be  necessary. 
Examples  of  work  of  this  character  that  may  be  mentioned  are 
cooperative  measures  for  the  collection  and  examination  of  rodents 
to  prevent  plague;  anti-typhoid  campaigns  in  urban  and  rural  dis- 
tricts, and  sanitary  surveys  of  interstate  and  international  waters  in 
relation  to  the  prevention  of  the  spread  of  typhoid  fever. 
There  is  necessity  not  only  of  quarantine  measures  to  prevent  the 
