314 Mr. Graham Brown. Intrinsic Factors in the [July 21, 



complicated by phases of relaxation. These finally cease, and the reaction 

 terminates with the extensor in a condition of maintained and unbroken 

 contraction. 



IV. Movements of Progression in the Low Spinal Preparation in which the 

 Muscles are De-affercnted. 



When the spinal cord is severed in the same manner in the de-afferented 

 preparation movements of progression may be obtained, and these are similar 

 to the movements observed in the preparation in which the afferent nerves 

 of the recording muscles are intact. 



In the record illustrated (see figure) the cord was cut approximately at the 

 point marked X in the figure on the signal line below (X, X also on the two 

 tracings). The first period lasts approximately up to the ordinates marked 1. 

 The upper tracing shews a state of maintained flexion broken by more or less 

 incomplete relaxations of short duration. The contraction of gastrocnemius 

 shewn in the lower tracing is unusual. The second period lasts approximately 

 up to the ordinates marked 8. The acts of flexion and extension are very regular. 

 Examination of the ordinates 4, 5, 6, and 7 shews that the commencement of 

 flexion is accompanied by gastrocnemius relaxation; the change from con- 

 traction to relaxation at the top of the tibialis anticus " beat " is accompanied 

 by a contraction of gastrocnem ius ; this does not last up to the point at which 

 flexion recommences. This contraction of gastrocnemius strongly resembles 

 the contraction of " rebound." The third period commences at or about the 

 point marked by ordinates 8, and persists up to the end of the record. 

 After the contraction of gastrocnemius marked by ordinates 9, the curve 

 begins to rise slowly. This is broken by a relaxation which commences 

 before the tibialis contraction marked by ordinates 10. This flexion move- 

 ment is small, and is not accompanied at its change to relaxation by a con- 

 traction of gastrocnemius. Thenceforth the gastrocnemius tracing exhibits 

 only periods of relaxation synchronous with the tibialis contractions, and no 

 rebound contraction. After ordinates 12 the gastrocnemius remains in 

 maintained contraction. 



The records thus shew the same three periods observed in afferent-present 

 reactions. 



In the first period the maintained contraction of the flexor muscle — com- 

 plicated by more or less incomplete phases of relaxation — is present. This 

 at first has sometimes been accompanied by little or no movement of the 

 extensor ; in other cases this latter movement has been present. 



The second period seems to be characterised by a greater regularity than is 

 usual in preparations in which the afferent arcs are unbroken. The movement 



