As part of the employment process, Marlow visits an old doctor who works for the company. What measurements does the doctor take and why? How does this meeting affect Marlow?
The old doctor Marlow had to visit before he deployed used "a thing like calipers and got the dimensions back and front and every way, taking notes carefully." The man is a phrenologist; he believes that the brain is divided into different "organs," each of which govern various beliefs and emotions. The more developed any given "organ" of the brain, the greater a person's propensity in that area. Further, they believed that you could thus determine a person's psychological makeup by feeling for lumps on the skull and measuring the cranium in various ways. (This "science" is not considered as obsolete and silly as the idea that a person's health and personality are governed by "humours" in the body.)
Marlow is annoyed by the meeting, but not so much because of the measurements, but because of the doctor's questions and off-hand comments. For example, he asks him if there is any madness in Marlow's family, a question Marlow considers unnecessarily intrusive.