Both Uses of

adopt
in
Misery, by Stephen King

Here was a Call clipping which said that the stray cat the student nurses adopted had been poisoned.†
Chpt 2 *

adopted = took on as one's own

Definition:

to take on as one's own

The exact meaning of adopt depends upon its context. For example:

"adopt a child" -- to legally take on parental responsibilities for another person's child
"adopt a plan" -- to accept or begin to use something
"adopt a pet" -- to take in a pet -- especially one from an animal shelter
"Congress adopted the resolution." -- had a formal vote and passed
"adopted a confident attitude" -- took on or displayed