Any guy can attest. Whether it's your head, your beard, your chest, or, um, anywhere else, your hair has a grain to it... a natural flow that never shifts, no matter how much you have or how long or short it is.
And, because of course he did, in 1902, Dr. Walter Kidd published "A Chart of the Human Hair Streams, Showing Their Lineage and History."
JF Ptak Science Books, a blog that presents "A Daily History of Holes, Dots, Lines, Science, History, Math, the Unintentional Absurd & Nothing" spied the map in an old journal, says,
There is something exceptional about the exceptional. In this case, the category is maps, and in this instance the map that takes us away, far away, from the expected or standard is one showing the flow of human hair streams...This unlikely title is the creation of Dr. Walter Kidd (Fellow of the Zoological Society, London) and his attempt to reconcile the the influences of gravity, inheritance, genetics, Weismannianism, and other assorted biological bits via his study of hair growth patterns... I should add that I was attracted to this article solely for the possibility that this may well be the first map of directional hair growth.