Enter your PIN <a href=" http://www.creativesummit.org/laxative-dulcolax-pregnancy#smash ">dulcolax dosage during pregnancy</a> Although Leonardo&rsquo;s interest in anatomy was not unique among artists, his scalpel-sharp observation, coupled with the lucid presentation of his findings, set him apart from his peers. &ldquo;Towards the end of his life, Leonardo was obsessed with the structure and functioning of the valves of the heart,&rdquo; says Clayton. &ldquo;So he made a glass model of the aortic valve, through which he pumped grass seeds suspended in water. And he witnessed little circular vortices in what&rsquo;s called the sinus of Valsalva, a sort of swelling at the root of the aorta. When blood flows through, these vortices play a role in closing the aortic valve. This is something that wasn&rsquo;t observed again until the 20th century &ndash; and Leonardo posited it in 1513.&rdquo;