6o PROTOPLASMIC ACTION AND NERVOUS ACTION 



A similar cycle of alteration is passed through, only 

 more rapidly, when the normal plates are transferred 

 from sea water to various unbalanced solutions, such as 

 pure isotonic NaCl; the plates then exhibit for a brief 

 period (one or two minutes) an extremely active vibratory 

 movement, which is associated with a progressive 

 whitening or coagulation. In general the rate of coagula- 

 tion is more rapid the more energetic the contractile 

 activity; and it is especially noteworthy that the coagula- 

 tive process does not begin until the plate starts vibrat- 

 ing; the vibration then continues until the whole struc- 

 ture is opaque. This change of structure is irreversible, 

 and at the end the plate is so altered in consistency that 

 it readily falls to pieces when shaken. Evidently the 

 contractile activity is associated with the removal of some 

 substance or condition which prevents the coalescence of 

 the protein particles forming the fibrils. A film-structure 

 of the kind suggested above seems indicated, which is 

 broken down by the action of the solution with the 

 production of both chemical and mechanical effects. 

 The general relations between such effects and stimula- 

 tion processes will be considered in more detail below. 

 Apparently in the swimming plate the essential effect 

 produced by the unbalanced solution is an acceleration 

 or intensification of the normal processes of stimulation 

 and contraction; a dependence of these processes on 

 the alteration or removal of film material is thus indicated. 

 The indications are that during the normal rhythm of 

 contraction in sea water the film-structure is alternately 

 broken down and reformed in each contractile cycle. 

 Presumably under the abnormal conditions resulting 

 from the action of the pure NaCl solution the rate of 



