Phoneix said:

<<well while we are on the subject or logic i am wondering.. if we sweat a 
lot 
and go into a hot/cold room we get really hot or cold....... well this makes 
the sweat hot/cold right???? well isnt sweat water???? so why dont the cursed 
of ranma & co. change??? (i.e. male ranma has been fighting kuno outside and 
the bell rings as he runs into the school he relizes it is really cold.... so 
since he is sweaty his sweat cools off and become cool/cold water....... why 
wouldnt this bring on a change into female form?)>>

Maybe the liquid has to come from an external source.  I was wondering does 
anyone know if snow changes Ranma into a girl?