TREITABILITr — CONTEACTILITY. 53 



or other movements with which we are acquainted at 

 all resembles these ? Observers have ascribed the 

 motion to a difference in density of different parts of 

 the mass, but who has been able to produce such 

 movements by preparing fluids of different density ? 

 But further, in the case of bioplasm or living matter, 

 these supposed fluids of difierent density in some un- 

 explained way make themselves and in some undis- 

 covered manner retain their differences in density ! 



82. Irritability — ContractUity. — Nor is it any ex- 

 planation of the movements to attribute them to 

 inherent "irritability," unless we can show in what 

 this irritability essentially consists. Some authorities 

 dismiss the matter by saying that the movements 

 depend upon the property of "contractility," but the 

 movements of bioplasm are totally distinct from " con- 

 tractility," such as is manifested by muscular tissue. 

 These remarkable movements take place in every 

 direction, and every movement differs from the rest, 

 while in muscular contraction there is a constant 

 repetition of changes occurring alternately in direc- 

 tions at right angles to one another. Hence, if the 

 movements in question be due to contractility, it is 

 necessary to admit two very different kinds of con- 

 tractile property, which are not of the same nature 

 and not due to like circumstances.* 



83. Movements fii the liioplasm of plants. — The 

 movements in the mucus corpuscle and in the amceba, 

 are of the same nature as those which occur in the 

 bioplasm of many plants, as is easily observed in the 

 cells of the leaves of the vallisneria or the anacharis, 

 in the chara, and in the hairs of the flower of Tra- 

 descantia ; and the appearance of the living matter 

 under very high powers is precisely the same in all 

 cases. 



84. Movements in morbid bioplasm. — Similar 



* See my paper " On Contractility as distinguished from 

 purely vital movements." — " Trans. Mic. Soe.," 18fi6. 



