"Many injuries to the brain from bullets of moderate size and low velocity do not cause more than a temporary loss of consciousness, and the subjects are seen by the surgeon, after the lapse of half an hour or more, apparently sound of mind.
These are the cases in which the ball has lost its momentum in passing through the skull, and has consequently done little damage to the brain-substance, excepting to make a passage for itself for a short distance into the brain. It is apparently well established that, in the case of the rifle-bullet of high velocity, and especially if fired from the modern military weapons using nitro-powders, and giving an enormous initial velocity to the bullet, the transmission of the force from the displaced particles of brain (and this rule applies to any other of the soft organs as well) to the adjacent parts is such as to disorganize much of the tissue surrounding the original track of the missile. Under these circumstances a much slighter wound would be necessary to produce unconsciousness or death than in the case of a bullet of low velocity, especially if it were light in weight. Thus I have recorded elsewhere an instance of instant death in a grizzly bear, an animal certainly as tenacious of life as any we have, from a mere furrow, less than a quarter of an inch in depth, through the cortex of the brain, without injury of the skull excepting the removal of the bone necessary for the production of this furrow. The jar to the brain from a bullet of great velocity, as in this case, was alone sufficient to injure the organ irreparably. In a similar manner I have known a deer to be killed by the impact of a heavy rifle-ball against one horn, although there was no evidence of fracture of the skull. On the other hand, game animals often escape after such injuries not directly involving the brain, although temporarily rendered unconscious, as I have observed in several instances, the diagnosis undoubtedly being concussion of the brain.
"Slight injury to the brain, and especially if it be unilateral, then, may not produce unconsciousness. It is not very uncommon for a missile from a heavy weapon to strike the skull, and be deflected without the production of such a state. Near the town in which I formerly practiced, the town-marshal shot at a negro, who resisted arrest, at a distance of only a few feet, with a 44-caliber revolver, striking the culprit on the side of the head.
The wound showed that the ball struck the skull and plowed along under the scalp for several inches before emerging, but it did not even knock the negro down, and no unconsciousness followed later. I once examined an express-messenger who had been shot in the occipital region by a weapon of similar size, while seated at his desk in the car. The blow was a very glancing one and did not produce unconsciousness, and probably, as in the case of the negro, because it did not strike with sufficient directness."Head Injuries with Loss of Cerebral Substance.--The brain and its membranes may be severely wounded, portions of the cranium or cerebral substance destroyed or lost, and yet recovery ensue.
Possibly the most noted injury of this class was that reported by Harlow and commonly known as "Bigelow's Case" or the "American Crow-bar Case." Phineas P. Gage, aged twenty-five, a foreman on the Rutland and Burlington Railroad, was employed September 13, 1847, in charging a hole with powder preparatory to blasting. Apremature explosion drove a tamping-iron, three feet seven inches long, 1 1/4 inches in diameter, weighing 13 1/4 pounds, completely through the man's head. The iron was round and comparatively smooth; the pointed end entered first. The iron struck against the left side of the face, immediately anterior to the inferior maxillary and passed under the zygomatic arch, fracturing portions of the spheroid bone and the floor of the left orbit; it then passed through the left anterior lobe of the cerebrum, and, in the median line, made its exit at the junction of the coronal and sagittal sutures, lacerating the longitudinal sinus, fracturing the parietal and frontal bones, and breaking up considerable of the brain; the globe of the left eye protruded nearly one-half of its diameter. The patient was thrown backward and gave a few convulsive movements of the extremities. He was taken to a hotel 3/4 mile distant, and during the transportation seemed slightly dazed, but not at all unconscious. Upon arriving at the hotel he dismounted from the conveyance, and without assistance walked up a long flight of stairs to the hall where his wound was to be dressed. Harlow saw him at about six o'clock in the evening, and from his condition could hardly credit the story of his injury, although his person and his bed were drenched with blood. His scalp was shaved, the coagula and debris removed, and among other portions of bone was a piece of the anterior superior angle of each parietal bone and a semicircular piece of the frontal bone, leaving an opening 3 1/2 inches in diameter. At 10 P.M. on the day of the injury Gage was perfectly rational and asked about his work and after his friends. After a while delirium set in for a few days, and on the eleventh day he lost the vision in the left eye. His convalescence was rapid and uneventful. It was said that he discharged pieces of bone and cerebral substance from his mouth for a few days. The iron when found was smeared with blood and cerebral substance.