i84 PROTOPLASMIC ACTION AND NERVOUS ACTION 



general effects are swelling, loss of consistency or turgor, 

 and disintegration of the tissue, accompanied by loosen- 

 ing of intercellular coherence; these effects are all 

 prevented or greatly decreased in the presence of a 

 little Ca. Hansteen believes that water-insoluble Ca 

 compounds are essential constituents of living protoplasm 

 in general, and that they are present especially in the 

 protoplasmic surface layers and other solid structures; 

 he also cites evidence indicating that these compounds 

 are lipoid in nature. According to his conception, 

 pure alkali salt solutions attack the surface layers of 

 cells because they alter the water-insoluble Ca-lipoid 

 compounds there present, converting them into water- 

 soluble compounds and secondarily inducing absorption 

 of water and structural breakdown. Such effects are 

 apparently of the same nature as the disintegration of 

 the cilia of marine animals (Arenicola) and the general 

 loss of semi-permeability of plant and animal cells in 

 pure salt solutions, already described. They are con- 

 sistent with the general view that in the formation of the 

 solid or permanent (water-insoluble) protoplasmic struc- 

 tures, Ca compounds play an essential part. Hansteen 

 found that the presence of more than the normal concen- 

 tration of Ca salts in culture solutions favored profuse 

 branching and the formation of an abundance of root 

 hairs in seedlings; Wiechmann, in Hober's laboratory, 

 has recently confirmed this result, and has found further 

 that Sr, Ba, and a few heavy metals (Mn, Ni, Co) act 

 similarly to Ca, while Mg is ineffective.^ It would 

 seem that certain necessary physical properties of 

 protoplasmic structures, such as rigidity, water- 

 ^ Wiechmann, Arch. ges. Physiol., CLXXXII (1920), 99. 



