FATTY  DEGENEBATIOK.  83

But  in  those  that  grow  fat  as  they  grow  old,  you  find,  in  all  the
tissues  alite,  bulk  with  imperfect  texture  ;  there  is  fat  laid  between
and  even  within,  the  muscular  fibres  ;  fat  about  and  in  the  fibres  of  the
heart,  in  the  kidneys,  and  all  the  vessels  ;  their  bones  are  so  greasy
that  no  art  can  clean  them ;  and  they  are  apt  to  die  through  fatty  de-
generation of  some  important  part,  such  as  the  heart,  the  minute  cere-
bral bloodvessels,  or  the  emphysematous  lungs.  The  defect  of  all  these
tissues  is  the  defect  of  quality.
Now,  I  do  not  pretend  to  account  for  this  great  difference  in  the
concomitants  of  the  other  infirmities  of  old  age  in  different  people.
The  explanation  probably  lies  far  among  the  mysteries  of  the  chemical
physiology  of  nutrition,  of  the  formation  of  fat,  and  of  respiratory  ex-
cretion ;  and  we  may  hope  to  find  it  when  we  know  why,  out  of  the
same  diet,  and  under  all  the  same  external  conditions,  one  class  of  men,
even  in  health  and  vigour,  store  up  abundant  fat,  and  another  class
excrete  the  elements  of  fat.  In  relation,  however,  to  the  present  sub-
ject, the  maiu  point  is,  that  the  similarity  of  the  conditions  in  which
they  occur  implies  similarity  in  the  essential  nature  of  the  two  changes,
and  that  the  defective  quantity  and  the  defective  quality  of  the  tissues
are  both  atrophies.
