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: In addition , VIP content of left ventricular muscle of resected failing hearts in 10 patients receiving a heart transplant was compared with the papillary muscles in 14 patients ( five with rheumatic disease , nine with myxomatous degeneration ) receiving mitral valve prostheses .
### Output Text:
In addition , VIP content of left ventricular muscle of resected failing hearts in 10 patients receiving a heart transplant was compared with the papillary muscles in 14 patients ( five with rheumatic disease , nine with myxomatous degeneration ) receiving mitral valve prostheses . 