A Note On Bicardial Circulation -- General

[A Moment In Subtext]

Doctor Who
A Note On Bicardial Circulation (or, Why Time Lords Really Are Superior To Humans Despite Or Potential And Their Extinction)
By. Cecilia Evans

"God gave man both reproductive organs and a brain, but only enough blood to run them one at a time."
We've all heard this saying; Its been floating around in some form or another (and with far less eloquence) for years, causing men everywhere to sigh, and women to smirk at Gods extraordinary sense of humour. This interesting thing is that this isn't a universal adage.
There are multiple species in when men lack one or the other (usually the latter) of these features, several lacking both, and even the odd species that lacks the basic genetic information necessary to form a non-female gender. However, the only species whose biologies are relevent to this sudy are Gallifreyan and Human.
In the Human Male (you may take Jack as your example), you have your Three B's: brain, bits, and blood. (Bisexuality doesn't count.) The blood is pumped from one heart, through one set of veins and arteries, to one destination. (Obviously, we all know which way our example's blood flows. Moving on now.)
The differences is that Time Lords (and the Doctor is your example for that, for simple reasons such as common awareness and the extinction of all the others) have Four B's: brain, bits, blood, and bicardiality. Two hearts, two sets of veins and arteries, two destinations. That's right, two destinations.
'Cos God likes the Doctor (sorry, meant Time Lord's in general there) so much better than us, He gave him (them) the ability to think during sex.