11 



What is the greatest simplicity of structure consisteut with the 



enjoyment of animal life ? 

 Powers of simple living animal membrane. 



It permits digestion Alimentary canal of man Absorp- 

 tion Medicines applied to the skin, and poisoned wounds 

 in amputated limbs. Respiration Back of frogs; ani- 

 mals throwing away their lungs; skin in man; effects of 

 cfeanliness; speed of race-horse. Nutrition Proof pre- 

 viously given Animal membrane constructs itself, and 

 fulfils the circle of the vital functions. 



Conditions necessary to the exercise of the functions of liv- 

 ing membranes. 



Theoretical condition of the simplest form of an animal A 

 sac of membrane full of a nutritive fluid, and endowed 

 with irritability and contractility. 



The simpler animals become, the more nearly they approach 

 this condition Remarks on Ehrenberg's discoveries 

 Objections to Cuvier's postulate of the necessity of nerves 

 to animal life Error of Lamark in terming the simpler 

 animals apathic (without feeling.) 



How nearly do the simplest animals approach to the theo- 

 retical stage of simplicity? Description and demonstra- 

 tion of a Medusa, or sea-nettle. 



Type of simplicity The hydra Description of its manners, 

 habits, and structure Composed of CELLULAR TISSUE 

 May be divided almost indefinitely, without destroying 

 the life of the pieces. A single hydra may be transform- 

 ed by art into a whole community of individuals with a 

 common life, attached to each other in a common mass. 



Cellular tissue Found in all animals Where? Descrip- 

 tion Illustrations Inflating chickens Consequences of 

 wounds of the lungs. 



Powers of cellular tissue. In the Hydra it fulfils all the 

 functions of an animal; even those of consciousness and 

 will without the aid of organs. Amusing proof. 



