i GENERAL PHYSIOLOGY OF MUSCLE 33 



Aplysia (Bottazzi), and those of the dog's stomach also show 

 automatic rhythmic oscillations of tone, similar to those in the 

 tortoise auricle, and may be explained by contractility of the 

 sarcoplasm, which certainly predominates in these muscles. 



More recently (1901) Bottazzi has endeavoured to extend his 

 hypothesis to all contractile protoplasm, including the striated 

 muscles of the skeleton. Why, he asked, should the muscular 

 tetanus due to the fusion of elementary twitches reach a height 

 considerably greater than that of a single twitch obtained from 

 the same muscle with maximal stimulation ? This is explained 

 by assuming that owing to the tetanising stimulus and the 

 weight applied to the muscle the muscular tone is exaggerated 

 into a contracture, which represents a form of " internal support " 

 maintained as long as the muscle remains shortened, while the 

 rhythmical contractions rise above the level of this contracture 

 (v. Kries, v. Frey, Grlitzner). v. Frey (1877) had demonstrated 



Fia. 24. Myograrn of frog's gastrocnemius loaded with 10'5 grms. (v. Frey.) t, t, myogranis of 

 tetanus ; s.i., s.i., myograms of simple contractions obtained with single shock of the same 

 induced current ; s.m.s., myogranis of a group of contractions obtained with the muscle 

 supported, i.e. relieved of the weight during relaxation. 



that on exciting the muscle of a frog by a series of induction 

 shocks, while the muscle is so supported that in relaxing it is not 

 stretched by the weight which it lifts in contracting, the con- 

 tractions rise in proportion as the lever-support is raised by a 

 screw, till they eventually reach the same height as the tetanus 

 of the same muscle, loaded and not supported (Fig. 24). 



But v. Frey's explanation is not sufficient. We still ask 

 on what does the contracture depend ? It cannot be due to 

 activity of the same contractile substance as that on which muscle 

 twitches depend, for it would then be unable to function as an 

 internal stimulus. Bottazzi holds that it can only be interpreted 

 on his hypothesis of the contractility of the sarcoplasm. He 

 assumes that the rhythmical faradic stimuli (and in our opinion 

 the weight which stretches the muscle as well) are capable, in 

 addition to the rapid twitches that summate in the curve of 

 tetanus, of evoking a further excitation and contracture of the 

 sarcoplasm, which constitutes an internal support. If after induc- 

 ing " veratrin contracture " in a muscle it is excited with a maximal 

 induction shock, the resulting twitch rises above the level of 



VOL. Ill D 



