222 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



are but very imperfectly acquainted with the structures on which 

 our remedies act, and the exact mode in which these are affected 

 by them. Day by day, however, our ignorance is dimmishing ; 

 and we may hope that ere long rational treatment will to a great 

 extent supersede blind empiricism. It not unfrequently hap- 

 pens at present that we meet with a case which bears a very 

 close resemblance to others which we have treated successfully, 

 and which nevertheless obstinately resists the remedies wiiich 

 we had previously found serviceable. Our failure astonishes 

 and vexes us ; but we are ignorant of its cause, and we can only 

 select some other drug by guess and try it : we cannot at once 

 choose the one which will have the desired effect. 



Pathology. — In order to choose a drug which will have the 

 effect that we desire to obtain, we must know where the morbid 

 changes are taking place, and what their nature is ; and we 

 must be sure that our medicine will act on the affected part, and 

 in such away as to counteract the disease. We must trace every 

 symptom which we see, back to its unseen source; every flush 

 on the cheek, every quickening of the pulse, back to the vaso- 

 motor or cardiac nerves, which have allowed the capillaries to 

 become dilated, and thus produced the redness, or have per- 

 mitted the heart to beat more rapidly than its wont. We must 

 then inquire what has produced this alteration in the nervous 

 system, and so on, till at last we discover, if possible, the hidden 

 cause of the mischief. We will then give that remedy which 

 will act in the proper way on the part which we believe to be 

 the seat of the morbid process ; and, if the expected result does 

 not ensue, we shall, at any rate, have discovered what the 

 pathology of the disease is not ; and, by trying a remedy which 

 will act in a different way or on a different structure, we may 

 find out what it really is. 



When I speak of the pathology of a disease, I do not mean 

 those obvious alterations in the structure of an organ which we 

 meet with in ;post mortem examinations, but the so-called func- 

 tional chanoes which precede and are the cause of both them 

 and the symptoms. For example, the disorganisation of a man's 

 liver by the presence of an abscess, or of his kidneys by fatty 

 degeneration, is not the disease from which he suffered, any 



