THE HISTORY OF THE SUBJECT 7 



futile conceptions, which equalled the phantasies of the worst 

 period of speculative philosophy and which in no way led to 

 progress. Hence it is easy to understand that numerous attempts 

 were made in those days to reconcile in some way these different 

 conceptions. An explanation, which was the beginning of fur- 

 ther development, came from England in the works of John 

 Brown (1735-1788),^ a man who was as talented as he was dis- 

 solute. Brown was an independent thinker, not without genius, 

 whose knowledge in practice and theory, however, was limited. 

 This combination in his mentality enabled him to observe the 

 problems somewhat differently than through the glasses of the 

 usual conceptions of that time. In direct opposition to his teacher 

 Cullen (1712-1790), one of the leading minds in the medical 

 school of Edinburgh, who considered irritability only as an 

 effect of sensibility and pronounced the latter a specific property 

 of the nervous system, Brown took the standpoint that all living 

 substance, vegetable as well as animal, in contrast to lifeless 

 matter, possessed a fundamental property which he designated 

 as excitability, that is to say, the capability of being stimulated 

 to specific vital manifestations through external factors or 

 "stimuli," in which sensitivity and indeed all mental processes as 

 well as movement are interpreted as specific effects, which the 

 "stimuli" produce on the irritable organs. This was an important 

 advance and from a wilderness of trifling conceptions his obser- 

 vations led to a clearer knowledge of this subject. But Brown 

 went even further. In his so-called "theory of irritation," he 

 has presented a whole system of responsivity to stimulation, which 

 in the first chapters of his chief work he expounds with wonder- 

 ful clearness. The fundamental principles here established must 

 be accepted even today. The essential basis of this "theory of 

 irritability" which he worked out especially for his doctrine of 

 disease, and which has also played an important part in pathology, 

 is the following: Every living, that is, excitable system, is con- 

 tinually influenced by stimuli. The stimuli consist of either exter- 

 nal factors, such as heat, food, foreign matter, poisons, etc., 

 or inner factors which result from the influence of the activity 



1 John Brown: "Elementa medicinae." 1778. English translation. London 1778. 



