MELANOPHOEE A TYPE OF SMOOTH MUSCLE CELL 211 



an irreversible coagulation as we find among suspensions or sus- 

 pension colloids. The presence of the fluid protoplasm in which 

 the granules are suspended must here be taken into consideration. 

 It is a well known fact (Bechhold '04) that the disperse phase of a 

 suspension colloid or suspension, adsorbs the particles of the dis- 

 perse phase of an emulsoid when the two are in 'solution' together. 

 This phenomenon has been termed a 'protection' of the coarser 

 phase; the adsorbed emulsoid is the protecting colloid ('Schutzkol- 

 loid' of Bechhold) . Under such circumstances, the suspension col- 

 loid assumes the character of a true emulsoid, i.e., it is protected 

 against the irreversible coagulative effects of electrolytes, heat, 

 etc. Suspension colloids or suspensions, in the presence of emul- 

 soids, thus become far more stable and plastic systems (Neisser 

 und Friedemann '04). The existence of just such a physical- 

 chemical system within the melanophore is a perfectly demon- 

 strable fact. Its reversibility is equally obvious. Thus far, 

 then, we have but analyzed the physical-chemical conditions 

 within the cell based upon the observed facts. 



In the case of an increased dispersion in a two-phase system, 

 there is an increased intimacy of relation between disperse phase 

 and solvent ; the system approaches a true solution and we speak 

 of an increased solubility of the disperse phase. Reciprocally, 

 in an aggregation or coagulation process, we have a separation 

 of disperse phase and solvent. There is an accumulation of evi- 

 dence at hand showing "that during the contraction of smooth 

 muscle there is an exchange of fluid between the cells of the tis- 

 sue and their surroundings" (Meigs ''12, p. 543). It is difficult 

 to imagine how this setting free of fluid can occur in a colloidal 

 system such as a smooth muscle cell, except in connection with a 

 reversible coagulation or aggregation process. In other words, 

 evidence for an exchange of fluid during contraction in both stri- 

 ated and smooth muscle must, at the same time, be considered 

 evidence for a reversible aggregation or coagulation process in 

 the cell colloids. The displacement of fluid is as necessary an 

 accompaniment of the act of contractio]i as is the coalescence of 

 colloidal particles.-' 



^ A discussion of the relative merits of the 'swelling' and 'surface-tension' 

 hypotheses of muscle contraction would be irrelevant (Lillie '12). 



