According to the results of clinical research, animals had hyperemic, swollen, painful, and sometimes moderately painful areas of the wound edges, walls and the surrounding tissues with  local febrile course, prior to treatment. Gaping wounds contained a large amount of purulent exudate of unpleasant odor, along with necrotic masses in their cavities. In some cases, there were recesses in the wounds that complicated their drainage. Histological examination revealed changes typical for abscesses formation stage in the affected tissue thickness. Clear distinction between the area of ​​lesions on the zone of leukocyte infiltration and the actual tissue of the dermis was observed. Necrotic detritus was detected in the lumen of the wound. The presence of signs of accumulation of tissue fluid indicates intense exudation and the development of wound edema.

At the 3rd day of the wound process in the experimental group dogs, there was a slight pain in the edges of the wound, moderate swelling and hyperemia around the wound tissue. Wound drainage was removed on average after 3-4 days of treatment which was 1.2 times (p <0.05) faster than that of the control animals. in Insignificant tissues swelling and hyperemia, as well as  pain of the wound site were observed in  animals of the control group on the 3rd day of the wound process. A small amount of purulent exudate was detected in the wound cavity . Wound drainage was removed, on average, after 4-5 days of treatment. Histological study in the experimental group animals reveal a clear demarcation shaft in the wound the border between healthy and damaged tissues, which characterizes the onset of the second phase of the wound process. The demarcation zone consists of macrophages and a small amount of eosinophils while in the control animals, the demarcation zone in the area of ​​damaged and healthy tissues did not have clear boundaries. There is detritus and thrombic mass in the wound biopsy. Inflammatory infiltration of the dermis in the wound area consisted mainly of leukocyte nuclei, fibrin and detritus.

The experimental group dogs were found to have no wounds swelling and hyperemia, and no pain reaction was observed on the 7th day of treatment. The presence of an epithelial rim indicated the end of the granulation stage. In average, sutures were removed after 9.0 ± 0.24 days of treatment (p <0.001) while in the control animals, there was a slight swelling and hyperemia of the wound edges and moderate pain was observed during the palpation on the 7th day of the wound process. Significant purification from necrotic masses was observed in the structure of the biopsies of animals in the experimental group on the 7th day of treatment. Pronounced regenerative processes of the basal layer of cells in the damage area ​ and the epidermis growth due to the reproduction of the producing layer were observed. Differentiation of fibroblasts and fibrocytes, with increase in the number of fibers producing cells, capillaries and blood vessels and in tissues that provide blood supply to the wound site takes place. On the 7th day of treatment in the control group dogs, a damaged skin segment containing purulent necrotic substrate with dead cells, with a large number of leukocytes in inflammatory infiltrates, was noted. The boundaries of the epidermis and the dermis are smoothed out. Slight regeneration of capillaries and vessels of different diameters was observed. Cellular composition in the thickness of the wound wall is polymorphic, leukocytes and cells with picnotial nuclei  were available, fibroblasts, fibrocytes, single fibrous structures appeared.

The results of the clinical study on the 10th day of treatment in the experimental group animals  indicate the complete end of the phase of inflammation and the development of regenerative processes. At the same time, pain reaction of parawound tissues was absent, moderate edema was maintained in the control group animals. Slight gape was found on some sites of the wound, the cavity was filled with granulation tissue. On average, sutures were removed on 11.2 ± 0.35 days of treatment.

Histologically, on the 10th day of the wound process in the experimental group animals, the bridging of the wound edges occurred. Epithelial layer of varying thickness prevailed on the wound surface, the epithelium almost closed the scar formation zone. Regeneration of skin derivatives  took place. The replacement of the wound defect with fibroblasts and fibrocytes, with different numbers of lymphocytes, was revealed. Differentiated blood vessels and vessels of a larger size were observed.

It was found in the structure of wound biopsy on the 10th day of treatment that the regenerating epithelium did not fully cover the scar formation zone in the control group animals. The replacement of a wound defect occurred at the expense of fibroblasts, which synthesized a significant amount of intercellular substance. The newly formed connective tissue contained granulation zones, as well as the remains of thrombogous masses that contained fibrin and destroyed leukocytes. At the boundary of the wound wall and bottom, the number of fibrous structures, small vessels, polymorphic cells increased.

By the 14th day of treatment a clear scar was been formed and there were sutures traces in the  experimental group animals, while the control group animals had no clear borders of the scar tissue and it was sometimes covered with scab.

Regenerated layers of the epidermis and dermis throughout the wound with characteristic structures of skin derivatives were observed in the structure of the wound biopsy of the experimental group animals on the 14th day of treatment. Also, newly created capillaries and vessels of different diameters were found. Partial uneven regeneration of skin tissues was noted in histostructure of tissue biopsies in the control group animals on the 14th day of treatment though the regeneration was not complete – a thin layer of destroyed leukocytes and fibrin remained sometimes. Recovery of blood vessels of different diameters was found, some were in the stage of formation.

According to the results of clinical trials, it was found that the use of succinic acid for the treatment of purulent wounds in dogs contributes to their faster purification from purulent exudate and to 1.2-times  (p <0.001) reduction in the duration of animals treatment compared with animals treated with 5% glucose solution.

Morphological study in the experimental group animals gives grounds to argue that amber therapy promotes a faster course of regenerative processes in the wound defection area. A decrease in the inflammatory infiltration degree and spread takes place along with acceleration of the granulation tissue and scar formation, more intensive tissue wounds with complete regeneration, the restoration of all skin structures with the appearance of differentiated connective tissue elements, compared with the control group animals.

We believe that further research should focus on the study of succinic acid drugs influence on of the wound process course in dogs.

Key words: succinic acid, purulent wounds, treatment, histological examination, clinical examination, dogs.