428 Xerz'oits Disturbances. 



degrees of contraction. A\'hen the members of the body are 

 thrown into motion by these contractions alternating with relaxa- 

 tion the spasm is said to be clonic (6 kUvos , violent movement) or 

 alternating; when the contraction persists for a longer time, 

 causing maintenance of rigidity in one position, it is said to be 

 tonic (0 TOfos. tension). Tonus and clonus may succeed each 

 other alternately. The mildest form of spasm is tremor, really 

 a quick succession of contractions of single muscles or muscle 

 groups, the coarser types evident as visible and palpable jerkings. 

 These muscular contractions or spasms are spoken of as convul- 

 sions when they give rise to excessive movement of the body 

 and limbs, or violent tremors of the whole body (Samuel). Tonic 

 spasm of individual muscles or of only one group of muscles is 

 also termed a cramp (as of the jaw-muscles, trismus, from rpl^ui, 

 to grit) : the powerful and long continued contractions of the 

 greater part of the musculature, tetanus ( reivu, to strain) ; a 

 general body rigidity, without any important contraction (merely 

 the ordinary contraction to maintain position), catalepsy; long- 

 continued shortening of individual groups of muscles, with perma- 

 ment deformity as a consequence, contracture (distinguished as 

 active, spastic or reflcxophile in distinction from the passive con- 

 tractures not of nervous origin met in disease of joints). Convul- 

 sions when accompanied by loss of consciousness are described 

 as epileptic or epileptiform. 



We know in connection with the causes of spasms that they 

 may be induced by a group of poisons or chemical irritants 

 (tetanotoxine, strychnine, ergotin, lead, carbonic acid gas), and 

 may be produced by poisonous substances arising as metabolic 

 products in the body (in uraemia), and that muscular contrac- 

 tions may result (directly or reflexly) from mechanical excitation 

 (section, torsion, crushing). In certain instances the spasms 

 are caused by local lesions of the peripheral nerves, of the cord 

 or of the brain (focal lesions), as the convulsions of suffocation 

 by lack of oxygen supplied to the medulla oblongata, those of 

 tetanus by the chemical combination of the toxine with the 

 nervous substance of the spinal cord. The more minute lesions 

 which take place in such examples are as yet not known, and the 

 extremely confused ideas we possess of the relations between 

 processes of excitation and inhibition prevent, for the present, 

 any satisfactory explanation of the conditions involved. 



The results of spasms vary with the location of the causa- 

 tive influence in the svstem. When the cause is directlv in the 



