796 THE POPULAR SCIENCE MONTHLY. 



Taken in this broad sense, " medicine " not merely denotes a kind 

 of knowledge, but it comprehends the various applications of that 

 knowledge to the alleviation of the sufferings, the repair of the in- 

 juries, and the conservation of the health, of living beings. In fact, 

 the practical aspect of medicine so far dominates over every other, 

 that the " healing art " is one of its most widely received synonyms. 

 It is so difficult to think of medicine otherwise than as something 

 w^iich is necessarily connected with curative treatment, that we are 

 apt to forget that there must be, and is, such a thing as a pure 

 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 characterized by its innate tendency to exhibit a definite 

 series of the morj^hological and physiological jDhenomena which con- 

 stitute organization and life. Given a certain range of conditions, and 

 these phenomena remain the same, within narrow limits, for each kind 

 of living thing. They furnish the normal and typical characters 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 ; abnormal 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 fr6m the typical life may vary indefinitely. They 

 may have no noticeable influence on the general well-being of the 

 economy, or they may favor 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 wathin the province of pathology. Ko sharj? line of demar- 

 kation can be drawn between the tw^o classes of phenomena. No one 

 can say w^here anatomical variations end and tumors begin, nor where 

 modification of function, which may at first promote health, passes into 

 disease. All that can be said is, that w^hatever change of structure or 

 function is hurtful belongs to pathology. Hence it is obvious that 

 pathology is a branch of biology ; it is the morphology, the physiol- 

 ogy, the distribution, the etiology of abnormal life. 



However obvious this conclusion may be now, it was nowise ap- 

 parent in the infancy of medicine. For it is a peculiarity of the physi- 

 cal sciences, that they are independent in proportion as they are im- 

 perfect ; and it is only as they advance that the bonds which really 

 unite them all become apparent. Astronomy had no manifest connec- 

 tion with terrestrial physics before the publication of the " Principia " ; 



