He spent much of his youth training himself in anatomical pathology and the various areas of natural science, gaining direct experience as a microbiologist, surgeon, and military physician.

[1] His father, Gustav Adolf Ignatz Rainer, emigrated to the Romanian Old Kingdom as an employee of the Strousberg Company that built the Bucharest-Giurgiu railway, the country's first.

Having performed numerous autopsies at the hospital, he made an original discovery himself; at the end of the thesis committee's debate, two of its members, Dr. Stoicescu from Colțea and Victor Babeș, extended their collegial greetings to Rainer.

The first, in 1906, involved work at Berlin's Frederick William University in the laboratories of Fedor Krause and Oscar Hertwig, as well as a study of embryology and comparative anatomy.

[21] Meanwhile, during this period, he was involved in scientific publication, sitting on the editorial board of Spitalul, writing for Romania Medicală and, in 1911, helping found the Paris-based Annales de Biologie.

[23] As Rainer himself noted, teaching was a major responsibility: "I have always held the belief that there is no feeling so great, no thought so vast and deep, that they may not reach out to young minds and hearts.

"[27] While in Iași, Rainer joined the left-wing literary circle formed around Viața Românească magazine, for which he contributed notes on medical science.

[36] Marta Rainer, who managed war hospitals, organized teams of surgeons to help deal with the humanitarian crisis, and operated non-stop during the extremely cold winter of 1917–1918.

[39] By late 1918, Rainer was conceiving of an education reform, aiming to compress theoretical aspects and "routine" work while providing students with as much laboratory experience as possible.

[43] After the general strike of 1920 was broken up by the authorities, Rainer was part of the investigative commission which determined that the labor organizer Herșcu Aroneanu had been beaten to death.

Rainer took personal charge of furnishing it, in the end setting up a large collection of craniums and full skeletons that earned the respect of Western colleagues such as Eugène Pittard,[46] Carleton S. Coon, Henri Victor Vallois, and Kurt Warnekros.

[47] He was seconded by his devoted disciple and godson, the endocrinologist Ștefan Milcu (he eventually left Rainer's team in 1932, after developing an allergy to formaldehyde).

At various intervals, the team also included surgeon Ion Țurai, pharmacologist Alfred Teitel, embryologist Benedict M. Menkeș, and anatomist Zalman Iagnov.

[50][52] After his move, Rainer began expanding the scope of his contribution, and passed on to his students a particular view of science, decisively materialistic, rationalist, and anti-metaphysical.

[55] The physician and left-wing political figure Ion Vitner writes that Rainer's understanding of the human body, heavily influenced by the work of Wilhelm Roux, centered on "life", "movement", "function", and ultimately "ontogenesis", rather than on the "static catalog" of 19th-century anatomy.

[58] This helped him and his students make groundbreaking discoveries in area such as the dura mater, cranial nerves, the lateral aortic lymph nodes, and the hypophyseal portal system.

According to Papilian, Rainer moved freely between subjects outside of his competence, including the paleontology of Leonardo da Vinci and the latest discoveries in astronomy.

[68] Also that year, Rainer made a noted contribution to biological anthropology, publishing his finds on the medieval princely remains dug up in Curtea de Argeș.

[70] Pursuing her own career in Bucharest hospitals, Marta was later a personal physician of Helen of Greece, wife of King Carol II of Romania.

[65] According to Vitner, Rainer was the diametrical opposite of a Iași rival, the racist and LANC affiliate Nicolae Paulescu, who stood for "dark and backward scientism".

[76] Nevertheless, as readers of his work suggests, Rainer helped preserve a balance in anthropology by also looking into environmental factors, thus questioning the ideological supremacy of scientific racism.

[83] While on location in Nereju, Drăguș and Fundu Moldovei, he expanded the canon of anthropometry, and began recording blood type, investigated the presence and spread of syphilis, and provided free medical consultations to the peasants.

At Fundu Moldovei, where some of the villages were entirely cut off from the outside world, Rainer found that up to 50% of his samples showed contamination with syphilis, forcing him to distribute reserves of neosalvarsan.

"[86] Rainer's anthropometric work, which used for a permanent record peasant photographs, in large part taken by Milcu,[87] remains a problematic aspect of Gustian sociology.

As noted by cultural historian Z. Ornea (based on Stahl's recollections), Rainer "carried out unperturbed his anthropometric research, although he was not an adept of racial science and had no idea of what this anthropometry and blood chemistry [...] were going to be used for.

[94] With his activity in academia, Rainer reacted against cronyism, taking a public stand against arbitrary appointments in teaching, and ruining his relationship with the establishment.

At one such incident in early 1938, Rainer stood unmoved at his desk as some of his fascist students, including the son of painter Nicolae Tonitza,[50] lit firecrackers and threw eggs in his direction.

Maintaining a philosophical correspondence with the medievalist Alphonse Dupront, who was stranded in occupied France, he described the Nazi age as an "empire of suffering", reaffirming his conviction in "the future of mankind".

[120] Despite other political obstacles and the communist rejection of anthropology as an "abstract intellectual game", cultural anthropologist Vasile Caramelea was able to obtain approval for further research, and expanded the institute's contribution to social science.

[123] In 1979, at Editura Eminescu, Brătescu and Mihai Neagu Basarab published Rainer's diaries and letters, which were received with great interest by the intellectual community, including Geo Bogza, Constantin Noica, and Nicolae Steinhardt,[124] but less enthusiastically by the general public.