John Bobst ask, "Does anyone know of any adverse reactions or cautions to 
take when
processing either PGA or PLLA?".

PGA or PLLA are both absorbable polymers and can be affected by many 
factors such as heat, light, liquids, etc..  However, I would recommend 
that you take some samples of each material and leave in the acetone and 
Spurr's for an allotted time and see what happens.  Our pilot studies 
indicated that both materials will begin to degrade in acetone and certain 
resins ( we did not test Spurr's).  Also, these materials can be sensitive 
to heat (at what temp does Spurr's polymerize?). You might want to consider 
a light curing resin for your embedding medium.
	You also stated that you were "fixing" the bone in 70% ethanol.  Is there 
any reason you are not using 10% formalin?  In my humble opinion, trying to 
fix a sheep spine in 70% ethanol is a disaster waiting to happen ( been 
there, done that!).  However, 70 % ethanol works well for long term 
"storage" of well-fixed bones.
	Hope you find this useful and please feel free to contact me for further 
info if needed,
	Linda Jenkins