CHAKACTEEISTICS OF THE ANIMAL BODY 



23 



They have been described by Wentworth as follows: First, cajjfl- 

 larity, or the power that makes water stand higher at the edges of a 

 glass than in the center, exerts a profound influence on the nature 

 of the chemical reactions that take place. One example will suffice : 

 A glass plate placed over a tumbler practically filled with water 

 may leave a small bubble of air beneath. Under the influence of 



Fig. 1. — Diiferent types of cells composing the body. . A, Typical cell show- 

 ing : c, centrosome ; /, food granules in the protoplasm ; n, nucleus ;n.s., nucleolus ; 

 B, complete cell; C, nerve cell with axon and dendrites; D, involuntary muscle- 

 fiber; E, endothelial cells; F, cUiated epithelial cells from trachea; G, stratified 

 squamous epithelium from the skin. (Jordan and Kellogg, Evolution and 

 Animal Life.) 



capillarity, however, this bubble can be easily replaced with water 

 by sliding the plate slightly to one side and allowing a few drops to 

 fall on the exposed surface of the water. Second, surface tension, 

 the force that permits water to "heap up" shghtly above the top of 

 a glass so that it is more than level full, or that lets a dry needle 

 float on the surface of water, keeps the compounds of different 



