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: Myocardial calcium concentrations also were decreased ( 11 . 2 , 8 . 3 , and 8 . 9 mg . per 100 Gm . of fat - free dry weight , respectively ) in the three treatment groups , being significantly decreased only in the last two .
### Output Text:
Myocardial <span class="chemical">calcium</span> concentrations also were decreased ( 11 . 2 , 8 . 3 , and 8 . 9 mg . per 100 Gm . of fat - free dry weight , respectively ) in the three treatment groups , being significantly decreased only in the last two . 