^ INTRODUCTION. 



the lower animals and plants. For the veterinary physician the study 

 of life in the domestic animals must be of the greatest importance. 



Every living body is organized, — that is. composed of instruments 

 or organs each one of which is destined to fulfill some special office in 

 the organism called its function, the sum of which functions constitute 

 the life of the individual. Other bodies met with in nature, and not so 

 constituted, are called unorganized, or inorganic, e.g., the mineral. 



Distinctions between Organized and Unorganized Bodies. — Organ- 

 ized and unorganized bodies have few or no correlative points, but stand 

 opposed to each other in almost every characteristic trait. 



Unorganized matter is only subject to the forces whose generality 

 of action constitutes physical and chemical laws. Organized matter is 

 also controlled to a certain extent by the same laws, and, although there 

 are a great many actions manifested by living bodies which are not 

 readily explicable by the ordinary physical laws, and for which the term 

 " vital phenomena" is conveniently employed, it does not by any means 

 follow that we have here to deal with any entirely distinct series of laws. 

 The attempt to reduce the so-called vital phenomena to physical and 

 chemical laws has already succeeded in demonstrating the dependence, on 

 physical and chemical principles, of many functions previously regarded 

 as purely vital in nature, and the hope may be reasonably held for con- 

 tinued progress in this direction. The sciences of physics and chemistry 

 are therefore the foundation-stones of modern physiology. 



Nevertheless, organized and unorganized matter differ to such an 

 extent that their consideration forms entirely distinct branches of study. 

 The forms, the forces, and the laws of unorganized matter are the sub- 

 jects embraced by physics and chemistry. The forms and forces of 

 living organized matter are the objects of physiological science, or 

 biology. 



Organic bodies differ from inorganic — 



1. In their Origin. — The former spring from a parent, or from 

 previously-existing living matter, either by splitting, budding, seeds, or 

 eggs. The latter have no such origin, but may arise from the combina- 

 tion, under the influence of chemical affinity, of the elements which com- 

 pose them. Spontaneous generation, though claimed by some, has not 

 been satisfactorily established. 



2. In their Form. — Organized bodies are usually determinate in 

 their form, rounded in their outline, and, in their simplest expression, 

 either spherical or spheroidal in shape. Unorganized bodies, on the 

 other hand, are irregular in their outline (amorphous), or, if determinate 

 in form, are bounded by plane surfaces and straight lines. 



3. Duration of Existence.— Organized bodies have a definite time 

 to live, pass through distinct stages of development and growth, and ulti- 



