Absurd
When the super injection began, Clovis didn't feel anything yet. He couldn't help but remember the feeling he experienced every time he injected the essence into his body.
At first, there wouldn't be any other sensation. But when more and more essence was injected, Clovis felt the heat building up in him as though his body was trying to neutralize the unknown object in his body.
Because of his low evolution rate, there was more essence that he needed to absorb, so it made the situation for him trickier.
If they injected too much, they would replace the liquid in Clovis's body too much, which might harm him or even kill him. That was why they were more careful with Clovis than the others.
Clovis gradually felt the heat in his body as his immune system was neutralizing the essence and tried to assimilate with it.