In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Renal function was assessed by biochemical ( plasma urea and creatinine ) , functional ( urine analysis and [ 3H ] inulin and [ 14C ] p - aminohippuric acid clearances ) and morphological ( degree of necrosis ) indices .
### Output Text:
Renal function was assessed by biochemical ( plasma <span class="chemical">urea</span> and <span class="chemical">creatinine</span> ) , functional ( urine analysis and [ 3H ] inulin and [ 14C ] <span class="chemical">p - aminohippuric acid</span> clearances ) and morphological ( degree of necrosis ) indices . 