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: The increase in intragastric pressure was directly related to the intensity of muscle fasciculations ( regression line : y = 0 . 5 + 4 . 78x with r of 0 . 78 ) .
### Output Text:
The increase in intragastric pressure was directly related to the intensity of muscle fasciculations ( regression line : y = 0 . 5 + 4 . 78x with r of 0 . 78 ) . 