 Lew's memories are intermingling with Thigs, making him feel what?
"With a psychic relay we will transfer the Earthman's memories and meager store of knowledge to the brain of Thig! So it was that the bodies of the Earthman and the Orthan were strapped on two parallel tables of chill metal and the twin helmets, linked to one another by the intricacies of the psychic relay, put upon their heads. An odd sensation, that his acquired memories labeled as pleasure, sent a warm glow upward from around his heart. Men had no mates on Ortha, sex had been overthrown with all the other primitive impulses of barbarism; so he was incapable of understanding the emotions that swept through his acquired memory.
 Discontent with his regular life as he becomes more enamored with Earth life.
 Worry. He begins to worry that he won't be able to separate from Lew properly later on.  Discontent with his regular life as he becomes more enamored with Earth life.  Anger at that state of Orthan civilization.  Worry. He worries that the Hord will no longer accept him when he returns.