INCOME OF MATTER 105 



for the view that leucocytes take some 

 part in these processes, as we find always a 

 great increase of these cells during absorp- 

 tion. Fat we have seen to be absorbed by 

 the lacteals of the villi. Ultimately the mole- 

 cules of fat reach the protoplasm in lymphatic 

 glands, and are there changed ; but probably 

 a portion of the fat is seized by special cells 

 in connective tissue (fat cells), and is stored 

 there in a liquid state. How it is used up by 

 the tissues is still obscure, but we may be 

 sure it contributes to the making of proto- 

 plasm in muscular, and more especially in 

 nervous, tissues. 



It is also difficult fully to explain the 

 changes that happen in proteins. At one 

 time it was supposed that peptones were 

 absorbed as such, and thus entered the 

 portal circulation. This view has been 

 abandoned, and now it would appear that 

 protein matter is absorbed in simpler forms 

 than peptones, and especially as amino- 

 acids. These are acids belonging to the 

 group known to chemists as fatty acids, 

 substitution compounds in which one of the 



