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 anatomical and aetiological diagnoses of peripheral nerve disease excluding its primary benign and malignant disorders , as seen in 358 Nigerians are presented .
### Output Text:
The anatomical and aetiological diagnoses of peripheral nerve disease excluding its primary benign and malignant disorders , as seen in 358 Nigerians are presented . 