<table>
    <tr>
        <td><span></span></td>
        <td><a><span></span></a></td>
        <td><span></span><span><span/></td>
    </tr>
<table/>

​$('td').find('span:first')

$('td').find('span:first');

<table>
    <tr>
        <td><span>span 1.1</span><span>span 1.2</span></td>
        <td><a><span>span 2.1</span><span>span 2.2</span></a></td>
        <td><span>span 3.1</span><span>span 3.2</span></td>
    </tr>
</table>

$("table td").find("span:first")