This form of dysmenorrhoea depends upon either a peculiar condition of the general nervous system or upon hyperæsthesia of the sexual system, or both combined. Either or both may have been inherited or acquired. It is frequent in subjects of the hysterical temperament, and in those presenting that preponderance of the nervous system so often seen as the result of over-refinement, luxury, habits of idleness, and other violations of hygienic law. Those subject to it often suffer from severe headaches, neuralgia, and other nervous affections. It is often caused by anæmia or chlorosis. Sexual influences, psychical or physical, and especially those that excite without satisfying, are sometimes efficient causes. Ovarian influence is often an important factor; some authorities designate all those cases in which no anatomical change can be found, ovarian. The prodromata of this form are very apt to be some of those nervous attacks to which such patients are liable, as headache or neuralgia, and they may be psychical, as aberration of temper, undue irritability, or tendency to melancholy. In character the pain is generally stated to be more acute than in the other forms. It is subject to great and sudden alternations. In acuteness and irregularity it often justifies the term spasmodic. From these characters and from the absence of anatomical change a differential diagnosis may be made. As in this form the most marked nervous symptoms are witnessed, so are also the most pronounced complications on the part of the general nervous system. They are often hysterical in character, but may be of every kind and degree, even to general convulsions, and mental aberration is sometimes a complication or result. Membranous dysmenorrhoea is characterized by the expulsion at the menstrual periods of organized membrane, either as a whole or in pieces. In the former case it is like a cast of the interior surface of the {197} uterus. The expulsion of this membrane is accompanied by pain, often of the most severe character. The pain presents well-marked features; it is markedly expulsive, identical with that of the obstructive form, closely resembling an abortion, to which the membrane adds an additional element of similarity. This pain and these expulsive efforts may continue twelve, eighteen, or twenty-four hours, and then cease, to be renewed only at the next period.