Sentence:  I can only assure you here that there "is" such a thing as a <WSD>nervous</WSD> child; whose nervous system is unstable; who is easily upset; whose pulse is apt to "run away" at any excitement; who blushes and pales and sweats easily; who tires easily; and who may be subject to headache and eye strain. 
Meaning of the word marked with <WSD> tags:  Easily agitated or alarmed; edgy, on edge.