170 REPORT — 18G6. 



tract. It should then be removed from the vapour ; and when it has become 

 fully extended, the tourniquet should be taken off; the blood will then 

 gradually find its way into the limb, and restore the flaccid elongated con- 

 dition. 



In this experiment we have the contrast of two limbs without blood, one 

 of which is under a contracting influence ; and we get an excess of chloro- 

 form in the tissues of one limb and protect the animal to a great extent from 

 being generally aiFected. As might be expected, this state of contraction 

 is never so easy to produce when an animal possesses its full complement of 

 blood ; for although the blood may be stagnant in the vessels, it will supply 

 for a considerable time the elements which oppose the coutracting-powers of 

 the chloroform ; hence, if we would produce the state of contraction under 

 such conditions, an amount of chloroform is demanded in the tissues which 

 ordinarily destroys the animal. But by adopting the plan of allowing the 

 ingress of the chloroform only through the limb which Ave wish to afl'ect, we 

 overcome this obstacle and retain the heart in such a condition that the 

 circulation can be restored and the contractive state dissipated when the 

 mechanical impediment is removed from the aorta. 



In concluding this paper, I propose to take a hasty survey of the various 

 aflections of muscular tissue as they have presented themselves in my expe- 

 riments. 



Let us take as an illustration the gastrocnemius muscle of the frog in the 

 elongated or uncontractcd state. 1. It may exist in this elongated or un- 

 contracted state mth all its dynamical powers in a state of integrity. This 

 is its normal condition, as we see it in the absence of stimuli. 2. It may 

 exist in this state when deprived of dynamical power, or, in other words, in the 

 absence of irritability. 3. Both these conditions of elongation may be asso- 

 ciated with softness or flaccidity of the muscular structure, — the former neces- 

 sarily so ; the latter not, as the fixity of rigor may prevail. 



Now let us take the same muscle in a state of complete contraction. 

 1. It may exist in this state of contraction with its dynamical powers per- 

 fect. This is true in those normal contractions which quickly give place to 

 relaxation. 2. It may exist in this state when deprived of dynamical power, 

 as seen in the forms of permanent contraction induced by warm water and 

 ethereal vapours. 3. In a state of softness, or in a hard coagulated state. 

 The soft state is represented by normally contracted muscle, severed from 

 one of its attachments. The hard state is induced by ethereal vapours and 

 extremes of temperature. 



As with the state of elongation, so with that of contraction, the truly 

 dynamical state is one of softness. 



The dynamical conditions on which irritability depends may therefore 

 exist both in the elongated and in the contracted state, and may also be non- 

 existent in both of these states. Properly speaking, irritability is no more the 

 tendency which a muscle exhibits to contract than the disposition it shows 

 to relax or elongate subsequently to contraction ; in fact a comprehensive 

 definition must include both these conditions. Nor is either of these states 

 to be regarded (as far as muscle alone is concerned) as conditions of rest ; 

 for they are both active states so long as the muscle is a vital structure, and 

 both inactive when the dynamical power of muscle are absent. 



As yet there seems to be no reliable experimental evidence to show that 

 muscle per se, ever contracts spontaneously, i. e. in the absence of a stimulus ; 

 but there are plenty of indications that the same agent is a greater stimulus 

 at one time than another ; nor is there anv evidence to show that muscl& 



