Diseases  of  Cattle  and  Sheep. 
553 
the  warm  close  days  during  the  spring  and  autumn  to  the  cold 
hoar  frosty  nights*  so  common  in  low  marshy  districts.  It  is 
very  probable  that  two  or  more  of  these  agents  may  act  so  as  to 
produce  the  disease.  These  doubts  do  not  apply  to  the  causes  of 
fevers  in  these  localities,  which  are  clearly  traced  to  the  effluvia 
from  marsh  miasmata. 
In  crowded,  ill-ventilated  cattle-houses,  miasms  of  a similar 
character,  for  aught  we  know,  are  constantly  evolved.  The 
chemist  cannot  discover  the  nature  of  any  of  these  aerial  poisons, 
but  their  effects  are  visible  enough  ; and  it  becomes  a serious 
question  to  consider  whether  many  diseases  thus  induced,  at  first 
enzootic  and  confined  to  certain  localities,  do  not  become,  under 
certain  conditions  of  atmosphere,  not  only  epizootic  but  infectious. 
The  murrain  of  1747,  of  which  it  is  stated  on  authority  that 
30,000  cattle  died  in  Cheshire  in  the  course  of  half  a year  (the 
marsh  districts  of  Lancashire,  Lincolnshire,  Nottinghamshire, 
and  Leicestershire  also  suffered  to  a most  alarming  extent),  is 
supposed  to  have  originated  amidst  the  marshy  lands  of  Flanders 
and  Holland.  But  of  the  origin  of  this  murrain  nothing  certain 
is  known.  The  same  difficulty  is  experienced  in  tracing  the 
origin  of  pleuro-pneumonia,  an  epizootic  pestilence  that  has  pre- 
vailed in  this  country  since  1842.  But  thus  much  is  certain  of  the 
latter  disease,  that  it  had  been  raging  in  Ireland  for  some  twelve 
months  before  this  period ; that  it  was  brought  to  the  English 
side  of  the  Channel  by  some  half-starved  Irish  cattle,  and  in  a 
very  short  time  found  its  way  into  Cheshire,  Shropshire,  Stafford- 
shire, and  Middlesex;  that  its  ravages  have  been  more  extensive 
in  marshy  districts,  and  in  ill-ventilated  crowded  cow-houses,  than 
in  any  other.  So  that  whether  these  epizootics  did  reallv  originate 
amidst  swamps  and  malarious  localities  or  elsewhere,  there  is  not 
a question  that  they  become  increased,  aggravated,  and  localized 
from  miasmatic  influences. 
The  Cheshire  farmers  relate  some  extremely  curious  instances 
respecting  the  pleuro-pneumonia ; that  of  its  visiting  one  farm, 
missing  the  next,  suddenly  appearing  in  the  second  and  fourth, 
* In  low  valleys,  during  the  months  of  May  and  October,  after  a hoar  frost,  red- 
water  is  frequently  seen.  The  difference  in  temperature  between  the  warm  day  and 
the  freezing  point,  hoar  frost  being  the  ice  of  air,  is  sometimes  as  much  as  20°,  25°,  and 
occasionally  30°. 
It  should  be  understood  that  cold  is  not  a fixed  temperature,  or  range  of  tempera- 
ture, but  something  considerably  below  the  temperature  of  the  body.  Thus  after  the 
body  lias  been  warmed  throughout  the  day  at  a temperature  of  60°,  it  would  very  likely 
suffer  from  lying  on  the  frozen  ground  at  32°.  I am  inclined  to  believe  that  dysentery, 
so  common  a disease  in  low  marshy  grounds  in  the  autumn  months,  is  frequently 
produced  from  disease  of  the  liver  and  abdominal  viscera  induced  by  cold,  causing 
congestion  of  those  parts,  and  from  the  previous  summer  heat  these  organs  are  very 
likely  to  suffer  in  this  manner.  Many  of  the  autumnal  diseases  arise  from  the  great 
variations  of  temperature  between  day  and  night,  and  from  sudden  changes  of  wind, 
and  these  take  more  effect  when  they  find  the  body  relaxed  by  previous  heat. 
