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: Only 5 of the 160 F2 pituitaries exhibited the hemorrhagic phenotype ; 36 of the 160 F2 pituitaries were in the F344 range of mass , but 31 of these were not hemorrhagic , indicating that the hemorrhagic phenotype is not merely a consequence of extensive growth .
### Output Text:
Only 5 of the 160 F2 pituitaries exhibited the hemorrhagic phenotype ; 36 of the 160 F2 pituitaries were in the F344 range of mass , but 31 of these were not hemorrhagic , indicating that the hemorrhagic phenotype is not merely a consequence of extensive growth . 