64 J. A. MacWILLIAM and W. J. WEBSTER. 



specially marked from wrist to elbow along the line of the 

 flexor digitorum sublimis. It seems to be centred in the 

 belly of the working muscle with a good deal of spreading, 

 but there is, as a rule, no referred pain in more distant parts ; 

 in one subject pain in the palm of the hand was complained 

 of. The pain goes on increasing progressively while con- 

 tractile activity is kept up ; there is no remission, as may 

 sometimes occur markedly in the normal arm, where, work- 

 ing with a suitable load, decided aching may develop at a 

 comparative early stage, to pass off more or less completely 

 at a later stage. 



It is to be noted that the pain, increasing to almost 

 intolerable severity in some of these experiments, arises from 

 exercise of a comparatively small amount of muscular tissue 

 — the limited portion of the flexor muscle engaged in moving 

 a single finger — in presence of an acute lack of blood supply, 

 involving urgent want of oxygen (anoxaemia) and its con- 

 sequences, with excessive accumulation of metabolic products, 

 acids, and other bodies. The pain is no doubt protective in 

 character, tending to limitation of effort and shielding the 

 muscle from being spurred on to further and injurious 

 activity. Discontinuance of further effort for short periods 

 does not remove the pain, but it is almost immediately 

 relieved — in a few seconds — by readmission of b'ood into the 

 limb by removal of the obliterating pressure of the armlet. 

 Contractile energy, on the other hand, recovers gradually and 

 slowly; it takes some time to be fully re-estabhshed, and 

 even then is apt to fail more readily than before on repetition 

 of the experiment. It is evident that the pain and the 

 depression of contraction force do not run parallel in the 

 ischaemic arm. 



Relation of Pain to WeaTiening of Contraction Force. 



The conclusion just stated is supported by the fact that in 

 the ischaemic arm the development of pain in the course of a 

 successive series of contractions is much greater in proportion 

 to the weakening of contraction force than in the arm with 

 intact circulation ; with an equally extensive cutting down 

 of the energy of movement in the two types of arm, as 

 shown by the ergograph tracings, there was sharp pain in 

 the ischaemic arm at a stage when there was only a tired 

 feeling with some aching in the normal arm ; pain and 

 weakening of contractile force were differently related to one 

 another in the two cases. 



It may be noted that in the normal arm slight aching or 

 local tenderness may last for some little time after the 

 exercise of the flexor muscle (as recorded by the ergograph) 

 has been discontinued, while in the ischaemic arm the sharp 

 pain disappears quickly on re-establishment of the circula- 

 tion. There is reason to believe that in fatigue following 

 severe muscular exertion under normal conditions (for 

 example, football, etc.) the muscular aching and tenderness, 

 felt for a considerable length of time afterwards, especially 

 in individuals out of training, are dependent on a mechanism 

 of production that is not identical with that of the pain 

 caused by working an ischaemic muscle. 



