What is the grammar explanation for 高くなり?


I'm trying to make sense of this sentence:

> 一寸法師の背が高くなり立派な青年になりました

It's from the 一寸法師 story.

I don't understand the word 高くなり. It seems so be takakunarimasu, the same
inflection but without the masu suffix.

Is that right? Is there any book that explains this? In the same story there
are other expressions with verbs conjugated as masu form without the masu
part.

