NEW YORK, Sept 3 (Reuters) - Economic growth depends on the productive use of investment and rejuvenation of "capitalistic animal spirits", but that is not taking place now, Bill Gross, the manager of the world's largest bond fund, said in his latest investment outlook letter on Wednesday.

"Cross your fingers, credit growth is a necessary but not sufficient condition for economic growth," said Gross, who manages the $223 billion Pimco Total Return Fund. "Economic growth depends on the productive use of credit growth, something that is not occurring."

(Reporting By Jennifer Ablan; Editing by Chizu Nomiyama)