Various standard text-books of human anatomy give essentially similar descriptions relative to the formation of the greater, lesser and least or lowest splanchnic nerves. The description given in Gray's Anatomy, twenty-third edition ( ' 3 6 ) , may be cited as typical : "The greater splanchnic nerve is formed by branches from the fifth to the ninth or tenth thoracic ganglia. . . . The lesser splanchnic nerve is formed by filaments from the ninth and tenth, and sometimes from the eleventh thoracic ganglia. . . . The lowest splanchnic nerve arises from the last thoracic ganglion."
From observations on dissections covering a period of years the authors have been repeatedly impressed with the apparent frequency in the variation of the gross origin of the splanchnic nerves as compared with the so-called "normal" mode of origin described in the standard text-books. So marked is this variation that it was considered sufficiently jmportant, from a morphological as well as surgical point of view, to determine the average pattern of formation and the types of variation found in 100 cadavers. A review of the literature fails to reveal any published data bearing on this subject.
The nerves were dissected out and diagrammatic sketches of them made by students in the Human Anatomy Laboratory, all dissections and sketches being carefully checked and verified by the authors. Only those bodies were used in this study in which both sympathetic trunks and their splanchnic branches were intact and not damaged by faulty dissection or pleural adhesions. No records were kept of the color, sex or age of