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: Those dosages ( greater than or equal to 10 mg / kg ) that inhibited mean NTE activity in the spinal cord greater than or equal to 73 % and brain greater than or equal to 67 % of control values produced severe ( greater than or equal to 3 ) cervical cord pathology in 85 % of the rats .
### Output Text:
Those dosages ( greater than or equal to 10 mg / kg ) that inhibited mean NTE activity in the spinal cord greater than or equal to 73 % and brain greater than or equal to 67 % of control values produced severe ( greater than or equal to 3 ) cervical cord pathology in 85 % of the rats . 