492 PROCEEDINGS OF SECTION D. 



Granted, therefore, the existence of these ion-proteid compounds, in 

 endeavoring to utilise them as a means of furthering our acquaintance 

 Avith the intimate processes underlying life phenomena, it is of prime 

 importance to try and obtain some idea as to their actual nature, and, in 

 the first place, to inquire whether the reactions towards electrolytes of 

 the living tissues themselves afford us any clue to the phj'sico-chemical 

 nature of the ion-proteid compounds. 



First, as regards the question of equilibrium, it is evident, from the 

 preceding discussion of the experimental basis of the ion-proteid theory, 

 that the ions introduced into the complex from the surrounding solution 

 must frequently be readily replaceable, the one by another. Thus if we 

 place the jellyfish Polyorchis in a mixture of oOcc. of three-eighths 

 molecular sodium chloride, plus 5cc. of three-eighths molecular mag- 

 nesium chloride, rythmic contractions of the swimming-bell will occur ; 

 but if we now add 5cc. of three-eighths molecular calcium chloride the 

 beats will at once stop (32). The active peristalsis of the intestine pro- 

 duced in rabbits by the intravenous injection of a minimal dose of sodium 

 citrate, fluoride, sulphate, tartrate, oxalate, or phosphate can be almost 

 entirely suppressed by the subsequent injection of an equal quantity of 

 eighth molecular calcium chloride solution (33). If an electric current 

 is led through a medium containing paramoecium, and the medium, is 

 such that they swim towards the anode, the movement towards the anode 

 may be immediately abolished, or even reversed and converted into a 

 movement towards the cathode, by the addition of a small amount of 

 calcium chloride (34) ; or, to carry our illustrations even further, the 

 crustacean Cyclops, which is indifferent to light, can be rendered positively 

 heliotropic by the addition to the medium in which it is swimming of a 

 small quantity of COj ; these in turn can be rendered indifferent in even 

 negatively heliotropic by the addition of NaOH, and we may repeat the 

 process as often as we please (35). Instances of properties manifested 

 by tissues in various solutions which are modified, abolished, or reversed 

 by the addition to the solution of another chemical substance might be 

 multiplied almost indefinitely. Attributing the properties exhibited by 

 tissues in these solutions to the various ion-proteid compounds formed — 

 when, for example, a tissue exhibits a certain property in a solution of 

 magnesium chloride, which property is abolished or reversed by the 

 addition to the solution of calcium chloride — it is an obvious probability 

 that the magnesium proteid formed in the first instance has been partly 

 or wholly converted into calcium proteid hy the addition of calcium 

 chloride. That the chlorine ions may also play an important part in 

 bringing about the result does not aft'ect our argument. In other words, 

 the ions in combination with the proteids of the cells are often readily 

 substitutable one for another, so that- as in most chemical reactions, the 

 mass of the reacting substances plays a part. If chiefiy magnesium salts 

 are present the greater part of the ion-proteid formed will be magnesium 

 proteid; if calcium salts are now added they will displace the magnesium 

 and combine with some or all of the proteid, according to the mass of 

 calcium chloride which is added. 



The sails of the heavy metals, such as zinc, lead, silver, etc., stand, 

 however, in a somewhat diff'erent relation towards proteids. When 

 added to a solution of proteid they usually form insoluble compounds 

 with it. When applied to tissues they usually cause irreversible changes 



