PROTOPLASMIC STRUCTURE 25 



regularly arranged groups, in which the individual micellae may consist 

 of similar or of different chemical substances, and may vary largely in 

 shape and in size. The micellae may unite in clusters within the group, 

 so that a group may consist of smaller groups, and these smaller groups 

 seem to tend to form chains. These little lines or chains unite in a net- 

 work, with large or small meshes, as the case may be. In these meshes 

 is the water which gives to protoplasm its important nature as a colloid 

 (on which many of the vital functions depend: see page 25). Nageli 

 discriminates three conditions in which the water of the colloidal proto- 

 plasm may exist in relation to the micellae: the water of constitution or of 

 crystallization, the water of adhesion, and capillary water. The first 

 is as proper a part of the micellae as is the water of a crystal; the water 

 of adhesion is that held close to the micellae by molecular attraction; the 

 capillary water is that lymph filling up the meshes of the network outside 

 the sphere of attraction of the micellae. Other substances besides water 

 may be firmly held to the micellae, such as calcium salts, dyes, nitrogenous 

 and carbohydrate substances previously dissolved. Growth is accounted 

 for in this way. 



On the other hand, W. B. Hardy has recently published a theory 

 based on the nature and activity of the ions. (Ions are groups of atoms 

 or dissociated parts of molecules which carry charges of electricity and 

 so by their presence make a solution an electrolyte. All circulating 

 animal and vegetal liquids are electrolytes, and these, being alkaline and 

 pervading the tissues, make the latter electrolytes and alkaline also.) 

 Hardy supposes that bioplasm is made up of groups of about ten thousand 

 complex molecules. These groups (termed "particles") are held by 

 electrical equilibrium in suspension in water. Protoplasm is thus a 

 " hydrosol," and a hydrosol of the reversible type. Each particle or group 

 of molecules, Hardy supposes, is surrounded by a double layer or zone 

 of ions charged with electricity, the repulsion between the particles 

 keeping up the normal fluidity of the protoplasm. When the difference 

 of potential is changed the density of the hydrosol is altered in part by 

 means of the chemical reactions between contiguous molecules, these 

 reactions altering the electrical status of the ionic zones surrounding each 

 particle. Thus we have coagulation and decoagulation. This theory 

 also, though unsubstantiated, has no little interest in view of the impor- 

 tance in physiology of the doctrines of the osmosis and solution of salines. 



The Chemical Composition of Protoplasm. If the physical structure 

 and action of protoplasm are involved in many doubts and almost as 

 many hypotheses, certainly its chemical composition is surrounded by 

 more. Not but that we know the chemical "elements" entering into 

 protoplasm, for these persist after its death and may be readily deter- 

 mined; nor yet but that some of the substances in protoplasm have been 

 identified. It is the exact chemical arrangement of these elements and 

 these complex substances, how they are combined and especially how 

 they differ in the living and the dead, that baffle the skill, ingenuity, and 

 deft technique of the biochemists. The last suggested problem is the 



