I don't know what she is measuring but I believe it would be best to remain very still while she is doing it.

From the 1914 Blue Book of Iowa Women:

Dr. Margaret Vampel Clark of Waterloo was born at Pleasant Ridge, Lee county, Iowa. She is the daughter of John Christian Vampel and Clara Sandganger. She received her early education in the public and private schools, receiving her classical education in the University of Wisconsin. Her professional education was received at the Woman's Medical College of New York Infirmary, and Hahnemann Medical College of Chicago. She took post-graduate work in London, Berlin and Vienna. She was ever an ambitious and conscientious student, and as a result is a woman of broad education, as well as having unusual professional knowledge and skill.

In her home state of Iowa, Dr. Clark and Mrs. Mary T. Watts achieved notoriety by coming up with a supposedly objective formula for grading children based on certain physical attributes. According to a 1913 article in the Woman's Home Companion, her formula included a "cephalic index," measured this way: "multiply width of head by 100 and divide by length. . . . 80 to 85 cephalic heads are preferable." I wonder if her formula gave women extra credit if they took on the appearance of a founding father.

We know nothing of the context of the photo, so for all we know she could be an admirably modern doctor of 1914, indignantly demonstrating the pseudoscientific nonsense of the previous century.

The only thing she could be measuring is skull radius (at the point she's measuring).

The device she's using is for measuring curvature. The outer two pins are rigid and the center is spring loaded. The little indicator shows how much the pin is depressed. These are often calibrated to indicate the radius of a circular curve that would fit the three points.

The big question is why she's measuring the curvature of the boy's skull.