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: There was no evidence of repair to the damaged medullary interstitial matrix , or proliferation of remaining undamaged type 1 medullary interstitial cells after the recovery period following analgesic treatment .
### Output Text:
There was no evidence of repair to the damaged medullary interstitial matrix , or proliferation of remaining undamaged type 1 medullary interstitial cells after the recovery period following analgesic treatment . 