368 



GENERAL PHYSIOLOGY 



brought into contact with these stimuli, likewise gradually draws 

 in its pseudopodia, the protoplasm becoming contracted into 

 numerous, small globules and spindles, which slowlyflowcentripetally 

 into the cell-body i (Fig. 159). 



Upon the effect of chemical stimuli upon ciliary motion, 

 Engelmann (79, 1) and Rossbach (71) especially have carried out 

 detailed investigations. Here also the greatest variety of sub- 

 stances, such as acids, alkalies and salts, carbonic acid and various 

 alkaloids, have like effects, which always consist in an augmentation 

 of the activity of the cilia or flagella, the rate of their beat being 

 considerably increased. The result is a considerable augmentation 

 of the motor effect, which can be clearly observed in free-living 

 ciliated cells, such as Infusoria, in a great acceleration of their 



Fig. 159. — Actinospliarlum under cJiemical stimulation. A, Unstimulated ; B, at the beginning 

 of the stimulation ; C, after the stimulation has continued for some time (the pseudopodia 

 are almost entirely drawn in). 



motion. After the addition of chemical reagents the Infusoria 

 by the strokes of their cilia rush madly through the field of view. 



Numerous chemical stimuli act upon the different forms of 

 muscle-fibres (myoids, smooth muscle-fibres, cross-striated muscle- 

 fibres) in a manner analogous to that upon naked protoplasmic 

 masses, by calling out contractions. If to a drop of water in which 

 many Vorticellce exist, waving their bodies gracefully upon their 

 extended stalk-muscles, chemical substances of the above-mentioned 

 kinds be added, all the Voriicello} immediately draw together, their 

 stalk-muscles suddenly contracting in their elastic sheaths, and 

 coiling up into delicate spirals (Fig. 160, h). Gross-striated muscles 

 likewise contract suddenly upon chemical stimulation. If, e.g., the 

 sartorius muscle of a frog, which forms a small band of nearly 

 parallel, cross-striated muscle-fibres, be clamped in a muscle-holder 



1 Of. Verworn ('89, 1). 



