92 ANIMAL EXPERIMENTATION 



III 



The animal body has been aptly compared to a country 

 composed of many separate and individual States. As the 

 citizens of one State differ from those of another State, so, 

 but in a greater degree, the cells of one organ in the body 

 differ from those of other organs. The liver and the 

 spleen are commonwealths, each with a characteristic pop- 

 ulation of cells. Anatomy describes the form and structure 

 of these various organs. 



Physiology is the study of the action of the organs as 

 individuals and as parts of a living whole. The anatomist 

 would describe the locomotive as it stands fireless upon the 

 track. The physiologist would study it in motion, note 

 the coal consumed, the water converted into steam, the 

 load drawn, the speed, the method of control. The anato- 

 mist describes the structure of the heart, measures its 

 weight, and states its position in the chest. The physiolo- 

 gist studies the functions of the heart, the way in which it 

 pumps the blood, the working of its valves, the sounds 

 that mark its beat, the passage of the contraction wave 

 from apex to base, the quantity of blood thrown into the 

 arteries, the nutrition of the heart-muscle, and the control 

 of the heart by the brain and the nerves. 



Pathology, or the science of disease, rests upon anatomy 

 and physiology. The pathologist studies the structure and 

 the function of diseased organs. As the alterations in 

 structure which arc the consequence of disease cannot be 

 recognized without accurate knowledge of the structure of 

 the organ in health, so the alterations in function which 

 are the symptoms and signs of disease cannot be recog- 

 nized without accurate knowledge of the function of the 

 organ in health. 



Practical medicine answers the patient's three questions: 

 What is the matter? When shall I be well? What shall 



