834 THE BIOLOGICAL SCIENCES AND MEDICINE. 



science of medicine a " pathology " which has no more 

 necessary subservience to practical ends than has zoology 

 or botany. 



The logical connection between this purely scientific 

 doctrine of disease, or pathology, and ordinary biology, 

 is easily traced. Living matter is characterised by its 

 innate tendency to exhibit a definite series of the mor- 

 phological and physiological phenomena which constitute 

 organisation and life. Given a certain range of condi- 

 tions, and these phenomena remain the same, within 

 narrow limits, for each kind of living thing. They fur- 

 nish the normal and typical character of the species, and, 

 as such, they are the subject-matter of ordinary biology. 



Outside the range of these conditions, the normal 

 course of the cycle of vital phenomena is disturbed ; ab- 

 normal structure makes its appearance, or the proper 

 character and mutual adjustment of the functions cease 

 to be preserved. The extent and the importance of 

 these deviations from the typical life may vary indefi- 

 nitely. They may have no noticeable influence on the 

 general well-being of the economy, or they may favour it. 

 On the other hand, they may be of such a nature as to 

 impede the activities of the organism, or even to involve 

 its destruction. 



In the first case, these perturbations are ranged under 

 the wide and somewhat vague category of " variations ;" 

 in the second, they are called lesions, states of poisoning, 

 or diseases; and, as morbid states, they lie within the 

 province of pathology. No sharp line of demarcation 



