Re: Why was there a white substance mixed with the red when I bled?

It's not uncommon to faint at the site of blood.  Even a small amount.  It
doesn't mean you should not pursue a career involving taking or looking at
blood.  I had a similar experience the first time I watched a cat undergo
declawing surgery.  I almost fainted; lucky for me, I was able to prevent
it by sitting down, lowering my head and taking a drink of water.  I went
on to work in veterinary medicine for 10 years and currently, I perform
surgery on mice in medical research.  I have have had many colleagues share
their stories of the first time they observed blood collection or surgical
procedures.  Of course, if it continues and you still don't feel
comfortable, then you should pursue other careers.

My first guess is that the shiny white substance you saw in the blood was
your eyes playing tricks on you and you lost conscience because you fainted
at the site of your own blood (which is nothing to be ashamed of).

Blood is red, there's no debating that.  After it settles in a blood
collection tube it will separate.  The bottom half of the tube will contain
all the red blood cells and be completely red, while the top portion of the
tube will be clear or slightly yellow and contain everything else; which is
mostly water mixed with clotting agents and other important stuff. SEE http://en.wikipedia.org/wiki/Blood_plasma  

If there is a lot of fat in the blood the top half of the tube may appear
white; representing fat in the blood.

The other possibility I thought of was inflammation under the skin in the
area of the needle stick.  

The bodies first defense against the presence of a foreign body is to
attack the area with white blood cells carried by the watery portion
(serum) of the blood.  Now I'm not saying white blood cells are white, but
when there is a localized infection and the white blood cells and serum
gather together, it results as a white material commonly known as pus. 

I hope this helps answer you question and relieves your spirit.

Here is a link to another good document describing the circulatory system: http://qldscienceteachers.tripod.com/biology/06human_physiology/03circulatory_system.pdf

Janet