138 RALPH S. LILLIE. 



going local chemical or electrolytic change in which insoluble 

 precipitates are formed. The rusting of iron is an example of 

 this general type of phenomenon, although here the deposits of 

 oxide, beyond showing a tendency to spread, i. e., to act as 

 centers for the deposit of new oxide, do not as a rule show struc- 

 tural peculiarities definitely suggesting an organic type of growth. 

 Certain other inorganic precipitates, however, such as the ferri- 

 cyanides of the heavy metals, especially when formed in the 

 presence of protective colloids like gelatine and egg-albumin, 

 may be deposited in a filamentous or vesicular form and give 

 rise to structures which are strikingly similar, both in morpho- 

 logical constitution and in the conditions of their formation, to 

 definite cellular or other organic growths. In the present paper 

 I propose to describe a number of methods by which these struc- 

 tures may be readily formed; and also certain methods of 

 accelerating or inhibiting their rate of formation, w r hich appear 

 to be closely analogous in their fundamental features to the 

 conditions controlling growth-processes in plants and animals. 

 Since these artificial growth-structures are beyond any question 

 produced by local processes of electrolysis, it seems justifiable to 

 regard the various parallels described below as affording strong 

 support to the above view that processes of a similar nature are 

 intimately concerned in the formation and deposition of struc- 

 tural and other materials in living organisms. 



II. EXPERIMENTAL. 



The formation of filamentous growths from an electrolytically 

 formed precipitate may be most readily demonstrated as follows. 

 A small piece of ordinary iron, e. g., a nail or tack or piece of 

 wire, is placed in a 2 per cent, egg-albumin solution (fresh egg- 

 white diluted six times and filtered) containing 2 per cent, 

 potassium ferricyanide (KsFeCye). Within a few seconds the 

 blue precipitate of ferrous ferricyanide is seen to form locally 

 at various spots on the surface of the metal; the precipitate is 

 deposited chiefly in the form of slender filaments which rapidly 

 increase in number and length until within fifteen to thirty 

 minutes the entire surface of the metal is covered with a blue- 

 green filamentous hypha-like growth. Alter a few hours some 



