Contrast  it  with  malarious  fever,  intermittent  or  remittent,  in  this  re-
gard. Let  a  healthy  man  sleep  in  a  solitary  rice  field,  a  desolate  jungle,
or  a  wild  swamp  in  a  summer  night.  He  will  almost  surely  be  seized
soon  after  with  disease  of  known  and  anticipated  type.  But  an  attack
of  cholera  can  only  be  procured  among  subjects  laboring  under  the
pestilence,  or  in  their  neighborhood,  or  as  infected  by  fomites  imbued
with  its  material  cause.  This  may  be  transported  with  persons  any-
where; it  remains  fixed  nowhere,  but  goes  and  returns.
Contagion  never  distinctly  detected,  as  I  have  said,  never  isolated  or
set  apart,  presents  itself  to  us  in  many  alleged  forms,  conditions,  and
modes  of  combination.
1.  In  the  newly-produced  fluids  of  the  exanthemata — the  lymph  of
vaccine  and  variola.
2.  In  the  pus  globules,  found  subsequently  in  the  pustules  in  these
diseases,  and  in  the  pus  of  syphilis,  gonorrhoea,  Egyptian  ophthalmia,
and  plague  bubo.
8.  In  the  ichorous  or  serous  exudation  of  herpes,  hospital  gangrene,
and  perhaps  of  erysipelas.
4.  In  the  hlood,  diffused,  as  in  scarlatina,  measles  and  smallpox.
5.  In  some  of  the  normal  secretions,  the  tears  and  saliva,  rendered
contagious  by  this  morbid  admixture,  as  in  measles,  and  in  the  lower
animals,  hydrophobic.
6.  In  the  cell — Langenbeck  and  Klencke  tell  us  they  have  repeatedly
conveyed  cancer  by  inoculation  with  the  cancer-cell.
7.  In  connection  with  the  presence  of  visible  animalculi,  especially
in  psora;  perhaps  in  chancre-pus  also;  and,  as  Velpeau  believes,  in
hospital  gangrene.
8.  In  connection  with  visible  though  minute  vegetation — algous  or
fungous,  as  in  tinea,  and  in  porrigo,  mentagra,  and  plica-polonica.
The  modes  of  application  in  and  through  which  contagions  exhibit
their  power  or  inicct  the  healthy  system,  arc  also  widely  various.
