AND PHYSIOLOGY. 



17 



fluid, with a saltish taste, and having odor, secreted from the 

 perspiratory glands. 



Elementary Tissues. 



58. Simple, or Basement Membrane.— 1. Simple Mem- 

 brane. This is usually a structureless layer of coagulated 

 albumen, often not more than 20000th of an inch thick. It 

 forms the walls of all cells, and is also spread out, as an in- 

 ferior layer of the skin and mucous membrane, and is then 

 called basement membrane. It is the most simple of all the 

 tissues, yet it is the agent of secretion, and sometimes of ab- 

 sorption, and these Professor Peaslee considers as its vital 

 properties, though of a low grade. 



59. Imbibition. — Simple membrane also possesses the re- 

 markable property of allowing fluids to pass through it when 

 it is placed between two fluids ; the effect depending in part 

 upon the electro-chemical relations of the substances, but not, 

 as generally supposed, on the difference of specific gravity 

 of the liquids. This is called endosmose and exosmose, or 

 Imbibition, and is the principal means by which fluids are 

 made to pass from one part of the system to another, where 

 no distinct vessels are provided for that purpose. 



60. Simple Fiber. — 2. Simple Fiber. This consists es- 

 sentially of threads of coagulated 

 fibrine, whose average diameter is 

 about g s'o 0 th of an inch thick. It 

 does not appear to be a permanent 

 constituent of the body, but only 

 a basis for the development of the 

 more complicated tissues. A good 

 example of the simple fiber may 

 be seen in the membrane lining 

 the inside of an egg shell, as in 



rig. 5. 



58. What is simple membrane ? How thick ? Where is it found ? What other nam© 

 is given to it? 59. Describe Imbibition. What purpose does it effect? 60. Describe 

 simple fiber. Its size. Where best seen ? 



