(56 J. A. MacWILLIAM and W. J. WEBSTER. 



the mechanical conditions connected with the fixed position 

 of the hmb and pressure on the skin of the finger by the loop 

 at the end of the cord which supports the weight. There is 

 evideutly a notable difference as regards pain production 

 between an alternately contracting and relaxing muscle doing 

 mechanical work and the condition of sustained tension neces- 

 sary to maintain tlie weight at certain levels. Similar results 

 were obtained with the abductor indicis. 



Relation to Pains of Angina Pectoris, Intermittent 

 Claudication, etc. 



It need hardly be pointed out that the foregoing observa- 

 tions have a close bearing on the problems associated with 

 the production of the pain of angina pectoris, showing as 

 they do how readily acute pain can be excited in skeletal 

 muscle working with lack of blood supply, the pain develop- 

 ing while the contractile power, though to some extent 

 weakened, is still sufficient to execute movements of con- 

 siderable range and energy — that is, long before complete 

 fatigue. 



There is every reason to believe that processes of the same 

 nature, with a similar production of pain of varying grades 

 of severity, up to the agonizing suffering of fully developed 

 angina, occur in cardiac muscle compelled to work with a blood 

 supply that is inadequate — absolutely or relatively to the 

 amount of work which the arm has to perform. Sir James 

 Mackenzie has emphasized the conception of anginal pain 

 as an expression of exhaustion of the cardiac muscle, 

 commonly associated with a defective coronary blood supply 

 and a susceptible nervous system. He has laid stress on 

 the production of the symptoms of heart failure— pain, breath- 

 lessness, giddiness, faintness — as expressions of impaired 

 functions of organs which fail to receive a blood supply 

 adequate to the needs of their normal activities in con- 

 sequence of a defective output of blood from the heart, 

 the latter itself suffering from insufficient blood supply 

 to its muscular walls; heart failure is thus recognized, 

 not by direct examination of the organ itself, but by the 

 functional effects of diminished blood supply to various 

 organs. 



It may be added that the results of the present experi- 

 ments have an obvious application to the phenomena of 

 the condition called " intermittent claudication," as seen 

 in the legs of men and horses, in which muscular exertion 

 is interrupted by attacks of pain, loss of power, coldness 

 of the limbs, etc. These symptoms can be definitely ex- 

 plaiued : in consequence of blocking of the main artery, or 

 disease or spasm of the vascular walls, the blood stream 

 has been reduced to such an extent tliat, while it may 

 suffice to supply the muscles in the resting state, it is 

 quite inadequate for their greater requirements during 

 activity — the results (pain, etc.) of the defective blood 

 supply are of the same nature and mechanism of produc- 

 tion as those demonstrable in the ischaemic arm of the 

 healthy subject. 



