In the sixteenth century Felix Plater[133] devised the following classification: 1. Mentis imbecillitas: Hebetudo, tarditus, oblivio, imprudentia. 2. Mentis consternatio: Somnus immodicus, carus, lethargus, apoplexia, epilepsia, convulsio, catalepsis, ecstasis. 3. Mentis alienatio: Stultitas, temulentia, amor, melancholia, hypochondriacus morbus, mania, hydrophobia, phrenitis, saltus viti. 4. Mentis defatigatio: Vigiles, insomnia. Linnaeus[134] in 1763 called his fifth class of diseases Mentales, divided into three orders: Ideales, Imaginarii and Pathetici. Sauvages in the same year included Hallucinationes, Morositates and Deliria under the heading of Vesaniae in his "Nosologia Methodica." Vogel[134] in 1764 divided Paranoiae into mania, melancholia, and amentia. Cullen in 1772 included insanity or the Vesaniae in the neuroses, divided into four groups—Amentia, Melancholia, Mania and Oneirodinia. He described eight varieties of melancholia and three of mania. Oneirodinia included somnambulism and nightmare. According to Jelliffe, Plocquet described six varieties of delirium in his treatise on paranoia in 1772. Pinel in 1791 limited himself to four classes of insanity—mania, melancholia, dementia and idiotism. He looked upon melancholia as a delirium exclusively directed upon one object or series of objects and accompanied by sadness. Idiotism was an advanced form of dementia. Esquirol in 1838 modified Pinel's scheme somewhat and described Lypemania, Monomania, Mania, Dementia and Imbecility or Idiocy. The active discussion of classifications of various kinds led Pritchard[135] to make the following interesting comment in 1822: "I cannot conceive anything more preposterously absurd than the attempt to classify diseases with all the divisions and technology of a botanical or zoological system, and to force what is essentially disorder and confusion to assume the appearance of that order and symmetry which nature displays in the arrangement of the organized world. An aetiological classification is the only mode of terminology and arrangement that can be of any practical advantage, and that is all that we have to consult." He nevertheless published a classification of his own which was essentially psychological in principle, although containing nothing new. The German school of this time was exceedingly prolific in the production of classifications, as will be shown by the following interesting and elaborate scheme of Flemming's[136] published in 1844:— FAMILY-AMENTIA—MENTAL DISEASES _First Group_—Infirmitas (Feeblemindedness). Varieties: A. According to etiology: 1. Inf. primaria, or congenita (Idiocy) 2. Inf. secundaria, or acquisita (Imbecility) a. Inf. e. morbo (Brain injuries, encephalitis, epilepsy, etc.) b. Inf. senilis