Inner Life

Leukocytes -- white blood cells -- normally flow around in blood unattached. An infection triggers signals that make the leukocytes move into tissue towards the foreign invader, in a process called extravasation. Extravasation needs specific interactions between the leukocytes and the endothilial cells lining the blood vessel. This process is visualized above. A longer version with biochemical commentary can be found here.

Exam Fever

Looking at these (sent in by a colleague), I was reminded of an old Beau Peep cartoon:

Officer: Are you familiar with the phrase 'flying colours'?
Beau Peep (salivating): Yes? Yes? ...
Officer: You failed with flying colors.