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: On Day 8 , the nerve - evoked peak twitch tensions , tetanic tensions , and fatigability , and the dose - response curves of d - tubocurarine in the tibialis cranialis muscle were measured in vivo and related to muscle mass or expression of AChRs .
### Output Text:
On Day 8 , the nerve - evoked peak twitch tensions , tetanic tensions , and fatigability , and the dose - response curves of <span class="chemical">d - tubocurarine</span> in the tibialis cranialis muscle were measured in vivo and related to muscle mass or expression of AChRs . 