In 1910, he defended his thesis "To the question of oxidative processes during pancreatic extirpation (an experimental study)", which he prepared in the laboratory of general pathology of Professor Oleksandr Repriov, a prominent pathophysiologist and endocrinologist, and received degree of Doctor of Medicine. In 1911-1912, D.P. Hryniov was on a two-year research trip abroad, working in Paris at the Pasteur Pasteur Institute in Paris and in Berlin. 

In 1912 he became an assistant at the Department of General Pathology (Pathophysiology), and in 1913 he was promoted to the rank of privat-docent and assigned to teach a course of bacteriology at the School of Medicine of Kharkiv University, where where an independent associate professor course in this section of microbiology had just been introduced. of microbiology. 

The question of which department should approve an associate professorship in bacteriology caused great controversy at the faculty. The departments of General Hygiene and General Pathology insisted on organizing this course. The following considerations were fundamentally important for making a decision in favor of one or the other department. 

Both departments, having the right to introduce such an associate professorship, determined the direction of microbiology development in different ways. The Department of General Hygiene, headed by Professor Stepan V. Korshun, already taught epidemiology and elements of microbiology as an optional course and considered it appropriate to add a sanitary and hygienic focus to microbiology. The Department of General Pathology introduced microbiology to a number of basic medical disciplines, directing its development towards the inseparable study of micro- and macroorganisms. The faculty accepted the point of view of Professor of General Pathology O.V. Repriov. On his recommendation, the faculty entrusted the teaching of the associate professor's course of bacteriology, which became obligatory, to D.P. Hrynev, Doctor of Medicine. Since that time, Damian Hryniov's activity was associated with teaching microbiology, which he successfully conducted for 21 years.

In 1914, D.P. Hryniov was elected a lecturer (head) of the Department of Bacteriology at the Kharkiv Women's Medical Institute. 

He was awarded the title of professor in 1916. 

At the same time, D. P. Grinev continued to teach an associate professor's course in bacteriology at the School of Medicine. The course occupied two small rooms in the laboratory of the Department of General Pathology. The equipment consisted of two microscopes, a thermostat and an autoclave. Bacteriology was taught in the third year and included 50 hours of lectures and 20-30 hours of practical classes. The theoretical course was disconnected from the practical classes: lectures were given throughout the year, and practical classes were held in cycles of 10-15 days, they were reduced to an elementary introduction to general microbiological techniques and did not even provide sufficient familiarity with individual representatives of pathogenic microflora. Lectures and practical classes were conducted by D. P. Hryniov, as the staff consisted of only a laboratory assistant and a minister. The preparation of visual aids - drawings, dead and live collections of microbes, preparations - was carried out directly by Hryniov with the help of students, his first graduates. In 1918, the position of assistant was introduced, which was taken by V.S. Derkach. The scientific work could not be widely deployed due to the lack of funds allocated for the needs of the course. In 1913-1920, six scientific papers were prepared and, in addition, a brief textbook on microbiology.

У 1918–1920 роках Д. П. Гриньов, на час відсутності професора О. В. Репрева, тимчасово завідував кафедрою загальної патології. 

In 1918-1920, D.P. Hrynev temporarily headed the Department of General Pathology during the absence of Professor O.V. Repriov. 

In 1920, when the School of Medicine of Kharkiv University merged with the Women's Medical Institute, D. P. Hryniov was elected as a president of the newly merged institution, which was named Kharkiv Medical Academy. 

One can imagine how difficult it was for him, a noble man, to get used to the abrupt transition from refined politeness to the harsh language of military orders. Nevertheless, he did not betray his motherland, did not go abroad to seek a better life, but stayed in cold and hungry Kharkiv, where he not only continued to train doctors that the nation desperately needed, but also did not stop his scientific work. Associate Professor S.H. Mironov, the author of a typewritten essay on the history of the Department of Microbiology, wrote in 1934: "He never left the department; during the civil war and the first difficult years of Soviet construction, no matter how difficult the conditions of scientific work were, Damian Petrovych never stopped it.remember the years when it was cold in the unheated laboratory, even with a coat on, and he visited the department every day and continued to work, being an example of resilience and efficiency for everyone."

Professor D. P. Hrynev served as president of the Kharkiv Medical Academy from July to October 1920. The term is short, but it should be noted that it fell on an extremely difficult period of history. In 1923, D. P. Hryniov was the vice-pro-rector of the Kharkiv Medical Institute (in November 1921, the Kharkiv Medical Academy was reorganized into the Kharkiv Medical Institute).

In 1922, the Department of Bacteriology of the Women's Medical Institute and the Bacteriology course of the School of Medicine were finally merged, resulting in the creation of the Department of Microbiology of the Kharkiv Medical Institute. The unification was facilitated by the fact that both departments were headed by D.P. Grinev. The organization of a single department contributed to the improvement of its material condition, because the department of the Women's Medical Institute had much better equipment, including 20 immersion microscopes. The department received large space for the educational process and research. 

In 1923, the department was already able to replenish its equipment with equipment imported from abroad. Since the early 30s, due to the attentive attitude to the needs of the department on the part of the director of the institute Dmytro Sergiyovych Lovli, as well as due to the receipt of funds from the Sanitary and Hygienic Institute, the Medical and Pedagogical Institute, the Dental Institute (Professor Dmytro P. Hryniov also taught a course in microbiology there), and the Ukrainian Institute of Experimental Medicine, one of the bases of which was the department, it became possible to purchase the necessary equipment, create a museum, a collection of drawings, drugs, etc. The department under the leadership of D.P. Hryniov became one of the best departments of microbiology in Ukraine. 

The teaching staff of the department was significantly increased. 

In 1934, it included one professor, two associate professors, seven assistants, and two laboratory assistants.

In 1934, the number of hours of microbiology teaching was increased to 160-220 at different faculties, which allowed for a significant expansion of teaching of general and special microbiology and, especially, sections on infection and immunity. It should be noted that in 1924, general microbiology was separated as an independent department, which taught second-year students; it existed for only two years under the leadership of Professor S.I. Zlatogorov, and then rejoined the Department of Medical Microbiology. In addition to the main medical faculty, the department also taught at other faculties. From 1924 to 1929, the Department taught a course in special microbiology for students of the Faculty of Odontology, and from 1930 - at the Kharkiv Dental Institute. During this time, a special course of oral microbiology was actually created, which was published by D. P. Hryniov as a textbook "Fundamentals of Oral Microbiology". It was the first textbook on oral microbiology in the Soviet Union.

Since 1931, the department has been teaching a special course in microbiology with practical classes for students of the Medical and Pedagogical Institute. Same year, the department began to teach a specialized course in microbiology at the Sanitary and Hygienic Institute. After this educational institution returned to Kharkiv Medical Institute and was transformed into the Faculty of Sanitary and Hygiene, the microbiology course saved its specialty.

Since 1934, the department approved a special course of food microbiology, which was entrusted to Associate Professor S. G. Mironov.

In different years, the department under the leadership of D.P. Hryniov also conducted advanced courses for students and doctors of the Institute for Advanced Training of Physicians, Stomatological, Sanitary and Hygienic, and Transport Medical Institutes. In addition, in 1931-1932, an epidemiology course was taught and classes were held.

The development of special microbiology courses and accumulated many years of pedagogical experience prompted the department and its head to prepare new textbooks. In addition to the aforementioned textbook by D. P. Hryniov, associate professor S. L. Utevska wrote a textbook for physician assistants. The two-volume work "Medical Microbiology" was prepared under the direct supervision of D. P. Hryniov, the authors of which, in addition to Professor D. P. Hryniov, were V. S. Derkach, S. G. Myronov, S. L. Utevska, R.Baranova, O. V. Chuiko. 

The improvement of the material base of the department, the training of personnel of scientific and pedagogical workers, the leadership of the exceptionally erudite and dedicated professor D. P. Hryniov contributed to the wide deployment of scientific and experimental work. During the period 1922–1934, the department published 74 scientific works, 9 popular science articles and brochures, and 3 textbooks. Most of them belong to the pen of D. P. Hryniov, prepared in co-authorship with him or under his guidance.

The main scientific problems studied by D.P Hryniov were the problem of tuberculosis, the role of oral microflora in pathology, and the problem of infection and immunity. Tuberculosis was a favorite problem of Damian Petrovich, which he was interested in throughout his scientific activities, devoting a lot of attention and energy to it. D. P. Hryniov's scientific authority, including at the international level, was extremely high. This is confirmed by a confidential letter received in the name of Mr. Professor D. P. Hryniov from Stockholm from the Nobel Committee in Physiology and Medicine of the Royal Caroline Medical and Surgical Institute. In this letter, members of the Nobel Committee suggested that he submit his proposal for the awarding of the Nobel Prize in Physiology and Medicine for 1935. The letter is dated September 1934. At that time, Damian Petrovych was seriously ill with an incurable disease, from which he died on October 10, 1934. The operation, which was performed by the eminent surgeon Professor V. M. Shamov in the presence of members of the Institute's Council, regarding the malignant neoplasm of the orbit revealed that it had grown into the meninges of the frontal area. So it was impossible to help the patient. 

On the problem of tuberculosis, 20 scientific studies were conducted at the department by D. P. Hryniov himself, with his direct participation and under his leadership, which mainly concerned the study of the metabolism of macro- and microorganism. The problem of tuberculosis was considered in various ways and thoroughly. Changes in blood, carbohydrate, nitrogen, water metabolism, synthetic and oxidative processes in experimental tuberculosis, glutathione metabolism in tuberculosis patients, etc. were studied. Premature death did not give D. P. Hryniov the opportunity to carry out the entire broad plan of research and interrupted the already started monographic work on the pathogenesis of tuberculosis infection.  

About the problem of infection and immunity, the department produced 19 papers devoted to the study of the mechanism of these processes in various infections. This direction was also introduced by D. P. Hryniov in the research work of the department and was developed with his active participation.

Damian Hryniov was an intelligent person with a huge scientific horizon, he knew German and French perfectly (read and wrote them). In his residence at 107 Osnovyanska Street, there was a large library and many of the books were printed in foreign languages, and he read them in the original. He loved and knew well the history of Russia and Ukraine, there were many historical books in his library. From the mentions of his relative V. A. Chuyk, we learn that he loved to travel, collected postcards with views of different cities, he had a whole collection of them. Sorting through them, it was as if he was going on a journey again. 

Damian Petrovych Hryniov devoted twenty-one years of his life to persistent, selfless work on the education of medical workers and the development of scientific research. His faithful student associate professor S. G. Mironov wrote: "From the moment the department was founded until the last days of his life, all his worries, all his attention were taken by the department and science." In order to perpetuate the memory of Professor D. P. Hryniov, in 1934, by a resolution of the People's Commissariat of Health, the Department of Microbiology of the Kharkiv Medical Institute was named after its founder and first head.

The Department of Microbiology, Virology and Immunology of the Kharkiv National Medical University is now proud to bear the name of Damian Petrovich Hryniov.

Reference: Гриньов Даміан Петрович — президент Харківської державної медичної академії (1920) / А. Я. Циганенко, З. П. Петрова // Керівники вищої медичної школи: Харківський національний медичний університет. – Харків : ХНМУ, 2020. – С. 75–80. 

Translated into English by Yevheniia Hromko