ON MUSCULAK IKRITABILITV. 171 



will contract on the -withdrawal of elongating inflnences, but abundance to 

 the contrary in the fact that it will remain in the elongated state in the ab- 

 sence of all susceptibility. Contraction and elongation would seem both to 

 be dependent on the existence of polar forces, which have a certain relation, 

 on the one hand, to excited nerve and external stimuli, and, on the other, 

 to some of the elements of the blood, — excited nerve and external stimuli in- 

 ducing the attractive, which involves contraction, and the blood the repulsive 

 polar attitude essential to elongation. 



The attractive state of the muscular molecules which represents contrac- 

 tion, is the condition in which force is exhausted by the association of unlike 

 polarities ; while the state of elongation being that in which every molecule 

 is opposed to every other, force may be accumulated. In proportion to the 

 amount of force accumulated in the molecules Avill be the intensity of their 

 contractive or elongative energy ; and also in proportion to their charge will 

 be their proclivity to disturbance — in other words, their susceptibility to 

 stimuli. 



When a stimulus can no longer act, it is because the force is exhausted. 

 If the chemistry of the muscle be not absolutely arrested, the power to 

 contract under a stimulus will return. If at the moment of its action a 

 stimulus be so excessive as to induce the attractive state of the molecules, 

 and at the same time to destroy the force-producing powei's of the muscle, 

 the molecules will remain in the state of approximation, simply because there 

 is an absence of any power to rearrange them. Conversely, if the force- 

 producing powers be destroyed during the state of elongation, the molecules 

 remain apart. 



Muscle, therefore, as a dead structure, has no tendency to remain in either 

 one or other of these states preferentially. The loss of irritability is the first 

 evidence we possess of a series of chemical changes which culminate in such 

 a coagulation of the muscular juices as to cause fixity, or setting of the 

 muscle. When these changes take place in the elongated muscle, the fixed 

 condition is produced which we recognize as rigor mortis ; when, on the 

 other hand, they take place in the contracted muscle, they induce the fixed 

 hard condition of the muscular structure seen in ethereal and thermal con- 

 tractions. 



Substances which affect muscular tissue may be classified as pure stimu- 

 lants, stimulo-coagulants, and depresso-coagulants. All substances possess- 

 ing the coagirlant property arrest the chemical reactions between the mus- 

 cular tissue and the blood, by which the fluid on which irritability depends 

 is generated. The stimido- coagulant class is represented by the irritant 

 action of chloroform and the ethers generally, and by extremes of tempera- 

 ture ; the depresso-coagulant by chlorine, carbonic acid gas, and the sedative 

 action of very dilute ether- vapour. 



It is possible, therefore, to have rigor mortis, or coar/ulative setting, in both 

 elongated and contracted muscles. 



While, therefore, my researches contradict the theory which refers the 

 phenomena of living muscle to statical electricity as an elongating power 

 simply, contraction being regarded as due to an inherent attractive power of 

 the muscular molecules, they are singularly in accordance with the con- 

 clusions of Du Bois Eeymond, who regards every elemental part of muscle 

 as a centre of electromotor action, containing within itself positive and 

 negative elements, arranged in a dipolar series, — and seem to fiU iip a gap, by 

 showing that the repulsive attitude of this series is maintained hy the blood. 



