388 GENERAL PHYSIOLOGY 



On the other hand, in the muscle mechanical tetanus can be 

 produced very easily. Vorticella, stimulated in the above-described 

 manner, passes at once into tetanus. The stalk-muscle remains 

 continually contracted. The tetanus is frequently so great that 

 the cell -bodies are loosened from their stalks and swim away. A 

 short time after the cessation of the stimulation the isolated stalks 

 extend again, but rarely continue to live for any length of time. 

 Cross-striated muscle can likewise be put into tetanus by a ham- 

 mer acting rhythmically and arranged to strike carefully upon the 

 muscle ; the latter remains contracted throughout the duration of 

 the stimulus. 



One might easily be misled by external appearances into re- 

 garding the tetanus of contractile substances as a phenomenon of 

 depression, for Amoeba, Actinosphcerium, muscle, etc., during the 

 tetanic condition are apparently in complete rest and motionless, 

 like the same objects when a narcotic has acted upon them. But 

 the two conditions have absolutely nothing to do with one 

 another. The difference is fundamental, as is shown by an investi- 

 gation of the metabolism. While in narcosis the metabolism 

 undergoes a real depression, researches have shown that in tetanised 

 muscle the metabolism is considerably increased. The decompo- 

 sition-products of the living substance, such as carbonic acid, 

 lactic acid, etc., undergo an extraordinary increase in quantity ; 

 certain substances that have accumulated in the muscle, such as 

 glycogen, become consumed ; and the production of heat 

 becomes increased to a considerable degree. It follows from 

 this that in the tetanic condition the vital process experiences 

 a considerable augmentation, that tetanus is a phenomenon not of 

 depression but really of excitation. 



The production of light by Noctiluca upon intermittent stimu- 

 lation appears to be a continual process analogous to the tetanus 

 of contractile substances. After a short time this phenomenon 

 decreases very considerably in intensity. 1 



~b. The Phenomena of Depression 



The phenomena of depression that are called out by mechanical 

 stimuli are as rare as the exciting effects of such stimuli are 

 manifold and wide-spread, and they have been little investigated. 



Horvath ("78), and later in agreement with him Reinke 

 ('80), made the statement that the growth of Bacteria the 

 cultures of which are continually exposed to regular shocks, is 

 interfered with, in other words a depression of groAvth takes place. 

 Later the validity of these experiments was called in question 

 by others; but recently Meltzer ('94), in a detailed series of 



1 Cf. Massart ('93). 



