You use the wrong CSS classes, try the following HTML:
<span class="icon-large icon-dog"></span>
When you inspect the source of the bootstrap.icon-large.css
file you will find out why:
.icon-large {
background-image: url("../img/glyphicons.png");
background-position: 24px 24px;
background-repeat: no-repeat;
display: inline-block;
height: 28px;
line-height: 28px;
vertical-align: text-bottom;
width: 28px;
}
.icon-large.icon-glass{ background-position: 0 0; }
.icon-large.icon-leaf{ background-position: 0 -34px; }
.icon-large.icon-dog{ background-position: 0 -69px; }