COMPARATIYE PHYSIOLOGY. 



GENERAL BIOLOGY. 

 INTRODUOTION. 



Biology (/3ior, life ; Xoyos, a dissertation) is the science which 

 treats of the nature of living things ; and, since the properties 

 of plants and animals can not he explained without some knowl- 

 edge of their form, this science includes morphology (jjuip^irj, 

 form ; Xoyor, a dissertation) as well as physiology (</)u(rts, na- 

 ture ; Xoyos). 



Morphology describes the various forms of living things and 

 their parts ; physiology, their action or function. 



General biology treats neither of animals nor plants exclu- 

 sively. Its province is neither zoology nor botany ; but it at- 

 tempts to define what is common to all living things. Its aim 

 is to determine the properties of organic beings as such, rather 

 than to classify or to give an exhaustive account of either ani- 

 mals or plants. Manifestly, before this can be done, living 

 things, both animal and vegetable, must be carefully compared, 

 otherwise it would be impossible to recognize differences and 

 resemblances ; in other words, to ascertain what they have in 

 common. 



When only the highest animals and plants are contem- 

 plated, the differences between them seem so vast that they 

 appear to have, at first sight, nothing in common but that they 

 are living : between a tree and a dog an infant can discrimi- 

 nate ; but there are microscopic forms of life that thus far defy 

 the most learned to say whether they belong to the animal or 

 the vegetable world. As we descend in the organic series, the 

 lines of distinction grow fainter, till they seem finally to all but 

 disappear. 

 1 



