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 the insulin - group the period of hypoglycaemia was associated with an increase in heart - rate and a fall in diastolic blood - pressure .
### Output Text:
In the insulin - group the period of hypoglycaemia was associated with an increase in heart - rate and a fall in diastolic blood - pressure . 