TISSUES. 69 



a proteid diet, but its production is more easily 

 prompted by a fatty diet and the carbohydrates. 

 Cold prompts its production, as is clearly manifest 

 in hibernating animals when the cold season ap- 

 proaches, and the increased weight of animals, as a 

 rule, during the winter season. 



Connective-tissue cell. 



Nucleus of fat cell. 



Fig- 35- Fat cells as they appear in sections treated with alcohol. 

 Alcohol dissolves the fat. 



The usual stain for fat is osmic acid, in which fat 

 acts as a reducing agent, precipitating black osmium. 

 Any reducing agent will do this, as is made evident 

 by the black color of the cork in a bottle containing 

 osmic acid solution, fat being absent from cork. 



Other connective-tissue cells, as Plasma cells, Wan- 

 dering cells, and Mast cells, are frequently described. 

 These resemble normal constituents of blood and 

 lymph to which they may belong. 



2. Connective-tissue Products. These products 

 may be a jelly-like substance or fibers. Connective- 

 tissue cells are always associated with these products. 

 There are two theories as to the production of fibers. 



(a) The fibers may be processes of the cytoplasm 

 that lose their cell connection. 



