8.  Specific  diseases  alone  are  capable  of  transformation  or  meta-
morphosis. As  we  watch  a  common  disease,  its  changes  seem  to  be
only  those  of  degree  ;  it  appears  increasing  or  declining,  but  is  always
the  same,  and  a  continuous  disease.  But  in  many  specific  diseases  we
see  changes  in  quality  or  kind,  as  well  as  in  quantity.  In  syphilis,  for
example,  a  long  series  of  diseases  may  occur  as  the  successive  conse-
quences of  one  primary  disease  different  from  them  all.  They  are  all,
in  one  sense,  the  same  disease,  as  having  a  single  origin  ;  but  it  is  a
disease  susceptible  of  change  in  so  far  as  it  manifests  itself  at  difierent
times,  not  only  in  different  parts,  but  in  different  forms  in  each,  and  in
forms  which  are  not  wholly  determined  by  the  nature  of  the  tissue
affected.  The  successive  phenomena  of  measles,  scarlet  fever,  and
many  others,  may,  I  think,  be  similarly  expressed  as  metamorphoses  or
transformations  of  disease.
9.  A  similar  transformation  of  specific  diseases  may  take  place  in
their  transference  from  one  person  to  another,  whether  by  inheritance,'

'  It  might  seem  as  if  none  but  specific  diseases  eonld  be  hereditary ;  but  many
tumours  are  so  which  we  cannot  well  call  specific :  Buch  as  the  cutaneous  cysts  or
■wens,  and  fatty  and  cartilaginous  tumours.
