386 M'Dowall 



a latent period of about "04 second) into the contracted condition ; but 

 relaxation occurs only very gradually and occupies a long time (fig. 2). 



4. In consequence of the length of the relaxation period, the summation 

 of stimuli can be produced and tetanus obtained by excitations which recur 

 at unusually long intervals (fig. 3). 



5. Within limits the amount of contraction is proportional to the 



Fig. 8. — Fatigue curve from ;i muscle which had been already completely fatigued and then 

 subjected to a prolonged period of rest. The curve on the right is taken after the muscle had 

 been more heavily weighted. (At the beginning of the experiment the stimuli were more 

 frequent than afterwards. ) 



Fig. 9. — Comparison curves from a muscle which had not been previously fatigued. 

 On the left unweighted, on the right weighted. 



strength of the stimulation (fig. 4 for single excitations and fig. 5 for 

 multiple excitations). On tetanisation with strong currents the muscle 

 contracts to as much as one-fourth of its oriofinal lenofth. 



6. As with other muscles, the periods both of contraction and of 

 relaxation are shortened by heat and lengthened by cold (fig. 6). 



7. The preparation lends itself well to the investigation of tlie effects 

 of fatigue (fig. 7), and especially to demonstration of the fact that muscular 

 fatigue may be recovered from, even in the mammalian preparation, with- 

 out the necessity for any call upon the circulating fluid. Thus a muscle 



