248 COLLOIDS IN BIOLOGY AND MEDICINE 



other suspensions (India ink, collargol) is the liver, spleen and bone 

 marrow. This was demonstrated by intravenous injection of stained 

 fat suspensions (lanolin with indophenol fat with scarlet R). 1 



In these organs there are certain cells which take up the fat par- 

 ticles (in the liver the star cells of VON KUPFER). It should be again 

 emphasized, that the fat particles behave exactly like inorganic 

 suspensions. They behave like inorganic suspensions, also as regards 

 rapidity of deposition; (depending on the size of the animal) after an 

 emulsion is poured into the blood (by alimentation or injection) one- 

 half hour to an- hour suffices for it to disappear from the circulation. 



It follows from the above that in the deposition of fat there is no 

 specific kind of fixation; that there is no solution but a purely me- 

 chanical retention of fat particles in these storehouses. 



How the storage of fat occurs in other organs, and how the mobili- 

 zation of fat reserves must be pictured, whether as an exceptionally 

 fine emulsion or a true solution, all these are still open questions. 



An especially instructive example of research regarding an assimila- 

 tion process is that of WOOD FORMATION. 



From a chemical standpoint, the lignified cells of the plant (wood) 

 consist of protoplasm, cellulose and lignin. While cellulose may be 

 considered as a distinct substance, a highly polymerized carbohydrate, 

 little has been known regarding the constitution of "lignin." Evi- 

 dently it is a mixture of various vegetable gums, pectins, lignic acid, 

 albumins, glucosides, tannins, vegetable coloring matter, resins and 

 other incidental constituents. A substance in lignin which is re- 

 garded as characteristic and which stains with anilin salts and 

 phloroglucin hydrochlorid was isolated by F. CZAPEK and identified 

 as an aromatic aldehyd. 



Various theories have been proposed to account for the formation 

 of wood; some placing more stress on physiological cnanges, and 

 others attempting to explain the process on a purely chemical basis. 

 I can dismiss these investigations in view of the fact that H. WISLT- 

 CENUS* has offered and experimentally established a theory which 

 places the entire view of this question as well as its experimented 

 investigation upon a new basis. 



He assumes that the cambial juice which penetrates the cambial 

 tissue stored between the wood and the inner bark layer during the 

 summer vegetative activity, contains crystalloids (salts, sugars and 

 plant acids) as well as colloids. These same colloidal constituents 

 (formative substance or procambium) are all found in the lignin. 



According to H. WISLICENTJS, the process of wood formation occurs 

 in three stages. 



1 For further references see S. BONDI and A. NEUMANN loc cit. 



