ON MUSCULAR IRRITABILITY. 157 



Report on Muscular Irritability and the relations lohich eoeist between 

 Muscle, Nerve, and Blood. By Richard Norris, M.D. 



Muscular irritability is commonly recognized and defined as that property 

 of niiiscular tissue by virtue of which it contracts under the influence of 

 stimuli. 



This property is said by Du Bois Reymond to bear a definite relation to its 

 electromotor powers. He says, " the diminution of the muscular current 

 after death is proportional to the diminution of the excitability of the muscle; 

 both the electromotor force and the excitability have the same tei'mination, 

 '('. e. in the rigor mortis, caiised, as Brueck has proved, by the coagulation of 

 the fibrin contained in the muscles external to the blood-vessels." As a 

 general summary of his researches on this question, Du Bois Reymond again 

 says, " the electric power of a muscle is always proportioned to its contracti- 

 lity, inasmuch as those agents which do not influence its contractility exert 

 no influence on its current." 



Matteucci has asserted " that the muscular current continually decreases 

 after the death of the animal, or after the sejiaration of the muscle from the 

 body " *. 



Taken in concert, these statements of Matteucci and Eeymond amount to 

 this : muscular ii-ritabiHty continually decreases after the removal of a muscle 

 from nervous and blood influences. This view of the gradual decline of 

 muscular irritability after somatic death is concurred in by physiologists 

 generally. Certain researches in which the author of this paper has been 

 long engaged, have led him to doubt the accuracy of this conclusion as a ne- 

 cessary and fundamental truth. 



As the consideration of the subject opens up a considerable range of ex- 



* By the death of an animal the author of this paper understands the loss of the pro- 

 perty of excitability or neurility on the part of the ganglionic nervous masses, without 

 power of restoration, in fact molecular death of the vesicular nervous tissue. It is certain 

 that the phenomena of life, as manifested by animals, may be again aroused into exhibition 

 BO long as the ca-pacity for molecular life ))ersists in the nervous system, notwithstanding 

 that both respiration and circidation may have long ceased. In a chapter on death, p. 905 

 of Carpenter's ' Principles of Human Physiology,' the following passage occurs: — " A surer 

 test, however, is afforded by tlie condition of the muscular substance ; for this gradually 

 loses its irritability after real death, so that it can no longer be excited to contraction by 

 electrical or other kind of stimulation ; and the loss of irritability is succeeded bv the 

 appearance of cadaveric rigidity. So long, then, as the muscle retains its irritability and 

 remains free from rigidity, so long we may say with certainty that it is not dead ; and the 

 persistence of its vitality for an unusual period affords a presumption in favour of the 

 continuance of some degree of vital action in the body generally ; whilst, on the other 

 hand, the entire loss of irritability and the supervention of rigidity afford conclusive evi- 

 dence that death has occurred. " 



On this the present writer would remark that although the persistence of muscular 

 irritability affords strong presumptive evidence of the existence of .systemic life, yet it 

 cannot be invariably relied upon, inasmuch as the irritability may in cases of excessive inter- 

 stitial change increase after the molecular death of the nervous masses and the final arrest 

 of the. Mood-current. On the other hand, universal rigor mortis, the result of the absence 

 of blood or suitable nutritional plasma, is a certain evidence of death whenever the circum- 

 stances of the case imply that the nervous system has also been subjected to a simultaneous 

 absence of itsjiroper nutrition, inasmuch as it appears to be a law without exception, that, 

 if muscular and nervous tissues be simultaneously shut off from their source of nutrition, 

 the molecular life of the nervous tissue is the fli-st to succumb. It is, however, possible 

 to conceive of certain spasmodic affections of the minute arteries supplying muscular 

 tissue in warm bloods inducing rigor rapidly, in the same manner as deligation of arterial 

 trunks ; and if at the same time it should happen from any collateral circumstance that 

 this condition of vascular spasm did not extend to the nervous masses, somatic death 

 ■would not necessarily be implied even by the existence of rigor. Universal putresceuce is 

 therefore the only absolute evidence of death. 



