363. Injuries to the Blood-vessels. It is very important to know the
difference between the bleeding from an artery and that from a vein.

If an artery bleeds, the blood leaps in spurts, and is of a
bright scarlet color.

If a vein bleeds, the blood flows in a steady stream, and is of a
dark purple color.

If the capillaries are injured the blood merely oozes.

Bleeding from an artery is a dangerous matter in proportion to the size of
the vessel, and life itself may be speedily lost. Hemorrhage from a vein
or from the capillaries is rarely troublesome, and is ordinarily easily
checked, aided, if need be, by hot water, deep pressure, the application
of some form of iron styptic, or even powdered alum. When an artery is
bleeding, always remember to make deep pressure between the wound and the
heart. In all such cases send at once for the doctor.

[Illustration: Fig. 157.--Showing how Digital Compression should be
applied to the Femoral Artery.]

Do not be afraid to act at once. A resolute grip in the right place with
firm fingers will do well enough, until a twisted handkerchief, stout
cord, shoestring, suspender, or an improvised tourniquet[53] is ready to
take its place. If the flow of blood does not stop, change the pressure
until the right spot is found.

Sometimes it will do to seize a handful of dry earth and crowd it down
into the bleeding wound, with a firm pressure. Strips of an old
handkerchief, underclothing, or cotton wadding may also be used as a
compress, provided pressure is not neglected.

In the after-treatment it is of great importance that the wound and the
dressing should be kept free from bacteria by keeping everything
surgically clean.

364. Where and how to Apply Pressure. The principal places in which
to apply pressure when arteries are injured and bleeding should always be
kept in mind.

Experiment 192. _How to tie a square knot_. If the student would
render efficient help in accidents and emergencies, to say nothing of
service on scores of other occasions, he must learn how to tie a square
or "reef" knot. This knot is secure and does not slip as does the
"granny" knot. The square knot is the one used by surgeons in ligating
vessels and securing bandages. Unless one knew the difference, the
insecure "granny" knot might be substituted.

[Illustration: Fig. 158.--Showing how a Square Knot may be tied with a
Cord and a Handkerchief.]

A square knot is tied by ho