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: During the SNP infusion the control animals demonstrated a progressive increase in blood pressure to 61 torr , whereas the saralasin - treated animals showed no change .
### Output Text:
During the <span class="chemical">SNP</span> infusion the control animals demonstrated a progressive increase in blood pressure to 61 torr , whereas the <span class="chemical">saralasin</span> - treated animals showed no change . 