lodged in the body of a soldier, the easiest way to extract it, and any attendant pieces of uniform, was with a finger. If too deep, a ball extractor could be used. The wound was then bandaged.
In the case of a head wound where access to the inside of the skull was indicated, the trepanning tool was used. This was essentially a hand drill that allowed a small disk of bone to be removed from the skull. Excess fluids could then be drained or other instruments introduced to reconstruct damaged bone. Since there was no anesthetic available, the wounded were wide-awake during these procedures. A stiff drink might be administered or perhaps some laudanum (a mixture of alcohol and opium). To prevent injury to the tongue the soldier might also be given something to bite on e.g. a stick, some leather or even a musket ball (hence the term to "bite the bullet").
As the germ theory of disease was still many decades in the future, no thought was given to sterilizing the surgical instruments. In any case, it was generally not possible to perform surgery under clean, germ free conditions. Infection was, therefore, inevitable. Remedies of various sorts might be tried but the infection generally had to run its course, hopefully not killing the patient in the process.
Rather than germ theory, medical personnel worked with the concept of humours. This theory suggests that there are four vital humours, or fluids, in the body that must remain in balance to maintain well being. Adjusting the amounts of these humours allows a diseased body to return to health. The four humours are blood, phlegm, yellow bile and black bile.
The correct quantity of blood, for example, can theoretically be maintained by the simple expedient of bleeding or blood letting. Applying leaches was one method of accomplishing this. Wet cupping was another. In this technique, several small incisions are made with a knife from the cupping set. A glass "bell" is heated over a candle and then applied to the wounds. As the air in the bell cools, the pressure drops, creating a partial vacuum, thereby drawing blood from the patient. To create many incisions at once, the spring-loaded blades of the scarifactor are used.
Given the serious nature of battlefield wounds and the crude level of treatment, did anyone actually survive the surgeon's ministrations? Perhaps surprisingly, yes! For example, for 146 major operations (shoulder joints, thighs, legs, arms) performed on soldiers in June and July 1815 in British general hospitals in Brussels, the survival rate was 78%. This may not be acceptable today but not bad for the nineteenth century!
It turns out that battlefield wounds were not the primary worry of soldiers on campaign: disease was. Far more soldiers died from the harsh, unhygienic conditions in camp than from actual battle. During the Peninsular War from 1812-14 the four major causes of mortality among British soldiers were as follows:
All things considered, we are much better off with twenty-first century medicine!
(statistics cited from Wellington's Doctors by Dr. Martin Howard)