Theodore H. Benzinger, 94, whose studies at the Naval Medical Research Institute led to a new means of measuring temperature in humans and whose inventions included the first ear thermometer, died Oct. 26 in the medical unit of the Maplewood retirement community in Bethesda. He had pneumonia and dementia.

Dr. Benzinger, who retired from the institute in 1970 as bioenergetics division director, made important contributions to temperature regulation research that helped open the field of biothermodynamics.

In work that continued at the National Institutes of Standards and Technology after he retired, Dr. Benzinger also expanded the fundamental theory of thermodynamics. He made a significant modification of the second law of thermodynamics--dealing with the distinction between spontaneous and non-spontaneous processes--as it applies to protein. That modification has come to be known as the Blanck-Benzinger equation.

His discoveries included the thermodynamic quantities of biochemical reactions as well as the mechanism of measuring temperature in humans. His invention 40 years ago of a highly accurate ear thermometer, since modified by other researchers, made it possible to zone in on the "human thermostat." He held patents for a dozen inventions in his field.

Life magazine, in a survey of significant inventions, featured Dr. Benzinger's human calorimeter, which measures heat gain and loss.

Dr. Benzinger was born in Stuttgart, Germany. He was a graduate of the University of Tubingen and received a medical degree at the University of Freiburg. He taught and did research before being named director of the aero-medical department of the German air forces testing center in 1934.

During the next decade, he studied decompression and respiratory and high-altitude physiology in pilots and also flew planes as a test pilot. Among his discoveries in this period was that of the air embolism as a cause of death from blasts.

Dr. Benzinger joined the Bethesda institute after World War II. His honors included an award for his work on calorimetry, the measurement of heat, given by the Chemical Society of Stockholm. Over the years, the society's Golden Scheele Medal has gone to a number of Nobel Prize-winning scientists.

He also was given the Senior U.S. Scientist Award of the Alexander von Humboldt Foundation, for a research year in Germany.

He wrote 136 scientific papers and chapters in 12 books.

Dr. Benzinger was a member of the American Physiological Society and the Aerospace Medical Association.

His marriage to Ilse Koss ended in divorce.

Survivors include his wife of nearly 40 years, Dr. Maria Benzinger of Bethesda; three children from his first marriage; a daughter from his second marriage; a stepson; a sister; six grandchildren; and two great-grandchildren.