CHAPTER XIII. 



THE AUTOGENOUS DISEASES. 



ALL living things are composed of cells. The simplest 

 forms of life are unicellular, and in these all the functions 

 of life devolve upon the single cell. Absorption, secretion, 

 and excretion must be carried on by the same cell. A 

 collection of unicellular organisms might be compared to a 

 community of men with every individual his own tailor, 

 shoemaker, carpenter, cook, farmer, gardener, blacksmith, 

 etc. However, only the lowest forms of life are unicellular; 

 all others are multicellular. In the higher animals there 

 is a differentiation not only in the size and structure of the 

 cells, but in the labor which they perform. The body of 

 man may be compared to a community in which labor has 

 been specialized. Certain groups of cells, which we desig- 

 nate by the term " organ," take upon themselves the task 

 of doing some special line of work, the well-doing of which 

 is essential to the health, not only of that group, but of 

 other groups as well, or of the body as a whole. There 

 is an interdependence among the various organs. Certain 

 groups of cells supply the fluids or juices which act as 

 digestants, and among these there is again a division of 

 labor. The salivary glands supply a fluid which partially 

 digests the starch of our food ; the peptic glands supply 

 the gastric juice which does the preliminary work in the 

 digestion of the proteids ; while the pancreatic juice com- 

 pletes the digestion of the starches begun in the mouth, of 

 the proteids begun in the stomach, and does the special 

 work of emulsifying the fats. But even some of these 

 products of complete digestion would be harmful should 

 they enter the circulation unchanged. The peptones must 

 be con verted into serum-albumin by the absorbing mechan- 

 ism of the walls of the intestines, and while 10 per cent. 



