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: Although moderate anticonvulsant effects of S - 312 - d in higher doses were observed against the clonic convulsions induced by pentylenetetrazole ( 85 mg / kg , s . c . ) or bemegride ( 40 mg / kg , s . c . ) , no effects were observed in convulsions induced by N - methyl - D - aspartate , picrotoxin , or electroshock in Slc : ddY mice .
### Output Text:
Although moderate anticonvulsant effects of <span class="chemical">S - 312 - d</span> in higher doses were observed against the clonic convulsions induced by <span class="chemical">pentylenetetrazole</span> ( 85 mg / kg , s . c . ) or <span class="chemical">bemegride</span> ( 40 mg / kg , s . c . ) , no effects were observed in convulsions induced by <span class="chemical">N - methyl - D - aspartate</span> , <span class="chemical">picrotoxin</span> , or electroshock in Slc : ddY mice . 