Jancowicz considers diagnosis possible only in typical cases, and expresses the opinion that paramyoclonus is a syndrome common to many affections. Further, Schupfer makes the perfectly justifiable remark that under this denomination have been included cases of chorea, tic, hysteria, and rhythmic spasm; others have been secondary to organic disease of the cerebro-spinal axis, such as rolandic lesions, spinal muscular atrophy, chronic poliomyelitis, syringomyelia. Others, again, depend on one or other of the psychoses, others on infective conditions such as malaria, diphtheria, typhoid, or on intoxications such as uræmia, mercurialism, or lead poisoning. Only a few recorded cases cannot be attributed to any of the conditions enumerated above, hence Schupfer's objection to the promiscuous classification of them all as paramyoclonus multiplex is quite warranted, in the absence of a uniform etiology and symptomatology. Schultze[184] has suggested the term monoclonus for the tics, and he distinguishes monoclonus, polyclonus, and paraclonus. Embraced in the last of these is the paramyoclonus of Friedreich, which, according to Schultze, is usually unilateral, voluntary action diminishing the intensity of the involuntary movements, whereas the converse is the case in tic or monoclonus. Mixed forms are met with, however, and Schultze himself mentions one in which the movements were bilateral and increased with voluntary activity. Heldenberg[185] applies the term intermittent functional myoclonus to twitches occurring from time to time in antagonistic muscles during voluntary movement, twitches exaggerated by excitement and diminished with rest. They occur in combination with well-marked vasomotor phenomena. The myokymia of Kny and Schultze is characterised by fibrillation, pain, hyperidrosis, and changes in electrical excitability. A case which seemed to be a combination of paramyoclonus with Thomsen's disease has been reported by Hajos[186] under the title myospasmia spinalis. There cannot possibly be any hesitation in arriving at a diagnosis between tonic tic and Thomsen's disease, a condition consisting in slowness of relaxation of a strongly contracted muscle, and conceivably due to defective metabolism or organic change in muscular tissue.[187] Examples such as the above, culled at random from an abundant medical literature, and variously entitled, will serve to demonstrate the protean nature of what the medical world is content to call myoclonus, and if from this collection of motor disorders we may hope to extricate the tics, there will remain still no inconsiderable labour of differentiation for the student. TIC AND ATHETOSIS The athetotic movements that may accompany hemiplegia are scarcely likely to be confused with those of tic, but difficulties may arise where the athetosis is double.