AND COMPARATIVE ANATOMY. 55 



Disease is a relative term, implying a comparison with a 

 state of health, and presupposing a knowledge of that state. 

 To anatomy, or science of healthy structure, is opposed 

 morbid anatomy, or science of diseased structure : to phy- 

 siology, or doctrine of healthy functions — pathology, or 

 doctrine of diseased manifestations. Morbid anatomy shews 

 us the diseases ; pathology, their external signs or symp- 

 toms. Often, no change of structure is observable : the 

 deviations from the healthy condition elude our means of 

 inquiry. The organ is said to be functionally disordered. 



Thus we iind that anatomy, physiology, morbid anatomy 

 and pathology, are mutually related and intimately con- 

 nected. Although called separate sciences, they are, in 

 truth, parts of one system ; and we must never lose sight 

 of their mutual bearings. On the foundation of these four 

 departments of knowledge or science is raised the practice 

 of medicine, or the healing art ; overlooking the artificial 

 distinctions of physic, surgery, and so forth. But is all this 

 knowledge necessary for a practitioner ? Is it required that 

 a physician or a surgeon should know anatomy natural and 

 morbid, physiology, pathology ? To the science of medicine, 

 and to its rational improvement and extension, it is neces- 

 sary ; but by no means so to the mere routine of practice, 

 and the very successful prosecution of the trade. Perhaps, 

 indeed, a firm faith in drugs and plasters, and a liberal ad- 

 ministration of them, may be the surer road to popular 

 success, if the remark addressed by a veteran practitioner to 

 a young enthusiast in science be well grounded ; " Juvenis, 

 tua doctrina non promittit opes : plebs amat remedia.'' 



A common sailor uses his glass without knowing the laws 

 of optics, or even suspecting their existence. But, would 

 Galileo have invented the telescope, and have given to 

 mankind the power of penetrating into space, if he had been 

 equally ignorant — if he had been unacquainted with the 

 action of various media, and of variously-shaped surfaces on 

 the rays of light ? An ordinary workman, of education and 

 habits purely mechanical, constructs the most powerful astro- 

 nomical instruments; but it belongs only to a Herschel or 



