On the basis of experimental results and clinical observations, the mechanism of injury and clinical features of wounds inflicted by modern weapons are evaluated from the view-point of wound ballistics. It is emphasized that, in order to accurately assess the injury, to formulate an appropriate treatment regime, and to prevent misdiagnosis, it is essential to learn the fundamental principles of wound ballis tics.

The processes of temporary cavitations produced with 7.62mm bullet, 5.56 mm bullet and 6.35mm spherical steel-pellet in water were recorded with a high speed (8,000 frames per second) camera to investigate the traumatic mechanism of fragments with high velocity and small mass. The temporary cavities produced with above mentioned projectiles were different because of their different ballistic behaviors. The shape and size of the temporary cavitv and the time of its formation were closely related to the density of the adjacent tissues and also to the extent of the tissue damage. Thus the study on the temporary cavitations after projectiles of high velocity but small mass is of clinical significance.

This paper is to report the study of the characteristics of the temporary cavitations produced by two kinds of bullets on the soft tissues of dogs. The diameters of the bullets were 5.56mm and 7.62mm respectively. And the experiments were performed on 35 dogs. High speed roentgenography of the injured parts was taken 0.268-5.690 ms after injury. It was found that the cavity produced by 5.56mm bullet was formed earlier, existed longer, and was accompanied heavier soft tissue damage than that produced by 7.62mm bullet. It was also found that the characteristics of the temporary cavity were closely related to the amount of the energy transmitted from the bullet to the surrounding tissues, the construction of the bullet and its ballistic behavior in the tissues.

The effects of the temporary cavities and pressure waves of peripheral nerves were studied following 5.56mm and 7.62mm bullets shooting the soap block and both thighs of dogs. The studies indicated that there was an exponential regression correlation among the displacement and stretching ratio of nerves and temporary cavity, the maximum of pressure peak(MPP), and energy absorption (EA). The degree of nervous injuries depended on the temporary cavity volume and amounts of EA. The amounts of EA of 5.56mm bullets were 40.67kg?m,2.5 times as much that of 7.62mm bullets.MPP of 5.56mm bullets was 1.8 times as of 7.62mm.This suggested that the nerve injuries caused by 5.56mm bullets were more severe than of 7.62mm bullets. Pathological examination showed that the microstructure of nerves was damaged though the microstructure unchanged. Fibre-broken-up, bleeding in perineurium, deformation of axon, mitochondria swelling and axon membrane dividing from its myelin sheath could be seen. In 5.56 bullet wounding group the potential latency was prolonged and the amplitude decreased remarkedly. This indicated that the nerves were only damaged partially. In early management it is important to release intraneural pressure, remove the hematoma in the fascia to recover microcirculation.

The pressure changes in water and in 20% gelatin blocks produced by bullets of 7.62 mm and 5.56 mm calibre and spherical steel balls of 1.03gm were studied. The pressure was measured by the BJ-100 model transducer.It was demonstrated that there were three peak waves produced when the two kinds of bullets were fired through a water tank. The interval between the two peaks was longer in the waves produced by 7.62mm bullet than in those produced by 5.56mm bullet, the value of The pressure due to 5.56mm bullet was the largest, that due to 7.62mm bullet was the second, and that due to the spherical steel ball was the lowest.The fore-mentioned differences among the pressures produced by different projectiles were closely related to characteristic ballistics of the projectiles. And the pressure value detected and the pattern of the pressure change vary with the transient space eifect and the characteristics of tissue damage.

To investigate the temporal variation of cell-mediated immunity in injured tissue of maxillofacial firearm trauma. Cells expressing messenger RNA(mRNA) for IL-2 were demonstrated by dot blotting and in situ hybrization in injured tissue of maxillofacial trauma inflicted by bullet, in conjunction with immunohistochemistry for IL-2 in normal and postinjury conditions. It was found that, apart from a transient eleratim in level within 24h post injury, both IL-2 production and IL-2 mRNA expression were consistently suppressed in cells at the site of the wound compared with the normal. The changes in the tissues of indirect injury by the projectile were significant. These results indicate that the cell-mediated immunity was suppressed in maxillofacial firearm trauma and the principal cellular abnormalities that resulted in altered T cell activation and IL-2 production postinjury was downregulation of mRNA before IL-2 gene transcription. It also suggested that the indirect injury by projectile contribute mainly to the depression of cell-mediated immunity.

The morphological and pathophysiological manifestations of theheart after abdominal gun-shot wound created by a model-53 smooth bore gun of 6.35 mm in caliber with 1.03 g steel ball were observed in 15 pigs,which were randomized into 3 groups.Five animals of the first group were killed immediately after wounding and all the animals showed small spotty flat hemorrhages on the endocardium of the left ventricle under gross inspection.Focal or small flat hemorrhages on the myocardium and under the endocardium were found under optical microscopy.Under electron microscopy,myofibrilla gaps were widened and filled with fluid,and mitochondrial swelling or vacuolar degeneration in the myocardium could be seen.7 animals of the second group were infused and monitored until they were killed 72 hours after wounding.It was found that there were varying degrees of functional disorder of the left ventricle in every animal.The serum level of creatine kinase isozyme MB increased significantly.The 3 pigs of the third group were killed with large andrapid blood-shedding without gun-shot wound and showed no similar pathological changes.

The injurious changes of the microvasculature in the maxillofacial region due to high-velocity bullet injury were observed in different time intervals with scanning and transmission electron microscopy. It was found that there were microthrombus formation in the vascular lumen, and endothelial loss and dege-neration or necrosis of the vascular wall in the microvasulature around the wound. Our findings indicate that when early reconstructive surgery for the tissue defect due to gunshot wound especially for those in the maxillofacial region is to be performed with microsurgical technique, it is essential for the surgeon to realize and consider the wounding condition on the microvasculature of the recipient site.

Histopathological and ultrastructural changes of the lungs were observed in various intervals after high-velocity bullet wounds of the two thighs of dogs. It was found that histologically there were microvascular dilatation, congestion, capillary rupture, interstitial and alveolar bleeding, focal atelecta-sis and pulmonary emphysema in the first half hour and the 6th hour after injury. In addition, microvascular embolism and hyaline membrane formation were seen in the 24th and 72nd hour after injury. Under electron microscopy, there were swelling of capillary endothelium, swelling, degeneration and necrosis of type I pneumocytes, shortening and decreasing of the microvilli of type II pneu-mocytes, significant vacuolation of the lamonar bodies, accumulation of leucocytes and platelets in the capillary lumen,and obvious decrease of the granules in the leucocytes. The mechanism of the pulmonary injury accompanying bullet wound of the thighs was discussed.

To investigate the temporal variation of cell mediated immunity in injured tissue of maxillofacial firearm trauma. Cells expressing messenger RNA(mRNA) for IL 2 were demonstrated by dot blotting and in situ hybrization in injured tissue of maxillofacial trauma inflicted by bullet, in conjunction with immunohistochemistry for IL 2 in normal and postinjury conditions. It was found that, apart from a transient eleratim in level within 24h post injury, both IL 2 production and IL 2 mRNA expression were consistently suppressed in cells at the site of the wound compared with the normal. The changes in the tissues of indirect injury by the projectile were significant. These results indicate that the cell-mediated immunity was suppressed in maxillofacial firearm trauma and the principal cellular abnormalities that resulted in altered T cell activation and IL 2 production postinjury was downregulation of mRNA before IL 2 gene transcription. It also suggested that the indirect injury by projectile contribute mainly to the depression of cell mediated immunity.