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 effect of amantadine hydrochloride , injected i . p . in 6 increments of 100 mg / kg each over 30 hr , on mouse motility and whole brain content of selected biogenic amines and major metabolites was studied in 4 strains of mice .
### Output Text:
The effect of <span class="chemical">amantadine hydrochloride</span> , injected i . p . in 6 increments of 100 mg / kg each over 30 hr , on mouse motility and whole brain content of selected biogenic <span class="chemical">amines</span> and major metabolites was studied in 4 strains of mice . 