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14  MAYO COLLABORATIVE SERVICES v. PROMETHEUS 

LABORATORIES, INC. 
Opinion of the Court 

2 
Other cases offer further support for the view that simp­
ly  appending  conventional  steps,  specified  at  a  high  level 
of  generality,  to  laws  of  nature,  natural  phenomena,  and 
abstract  ideas  cannot  make  those  laws,  phenomena,  and 
ideas  patentable.  This  Court  has  previously  discussed  in 
detail  an  English  case,  Neilson,  which  involved  a  patent
claim that posed a legal problem very similar to the prob­
lem now before us.  The patent applicant there asserted a 
claim 

“for the improved application of air to produce heat in 
fires, forges, and furnaces, where a blowing apparatus
[The  invention]  was  to  be  applied  as
is  required. 
follows:  The  blast  or  current  of  air  produced  by  the 
blowing  apparatus  was  to  be  passed  from  it  into 
an air-vessel or receptacle made sufficiently strong to 
endure  the  blast;  and  through  or  from  that  vessel  or 
receptacle  by  means  of  a  tube,  pipe,  or  aperture  into 
the fire, the receptacle be kept artificially heated to a 
considerable temperature by heat externally applied.” 
Morse, 15 How., at 114–115. 

The English court  concluded that the claimed process did
more  than  simply  instruct  users  to  use  the  principle  that
hot  air  promotes  ignition  better  than  cold  air,  since  it
explained  how  the  principle  could  be  implemented  in  an
inventive way.  Baron Parke wrote (for the court): 

“It  is  very  difficult  to  distinguish  [Neilson’s  claim] 
from  the  specification  of  a  patent  for  a  principle,  and 
this at first created in the minds of some of the court 
much difficulty; but after full consideration, we think 
that  the  plaintiff  does  not  merely  claim  a  principle, 
but a machine embodying a principle, and a very val­
uable one.  We think the case must be considered as if 
the principle being well known, the plaintiff had first