Codliver oil

My mate likes to smoke cannabis ,
he comes round mine and rolls it on my table,
the same old routine everytime, 
he uses big papers instead of making a deck
then he gets a thin piece of cardboard;
and puts it in the end in place of a filter,
I can envisage this in my sleep,
seen it done many times. 
one day he came in as usual,
began rolling,
then he took out a bottle of Codliver oil
and sprinkled some of the contents onto his weed,
I said to him;
"what's that for ?"
he replied " I watched a documentary last night,"
"and it said that Codliver oil is good for your joints !"