18 GENERAL PHYSIOLOGY 



question, and added the experimental proof of the fact that the 

 muscle-fibre possesses the property of contracting upon stimula- 

 tion independently of nervous influence, a quality which he sharply 

 distinguished as irritability from the sensibility belonging to nerves. 

 This sharp distinction affirmed a difference between the excitation 

 of nerve and that of muscle which did not correspond wholly to 

 reality, and awoke in many of Haller's adherents and followers the 

 need of demonstrating irritability to be a uniform phenomenon. 



This was attempted most successfully by an Englishman, John 

 Brown (1735-1788), a gifted but careless thinker. Brown recog- 

 nised in general a single excitability common to the nervous and 

 muscular system, which system he regarded as a unit. The ca- 

 pacity of becoming excited by stimuli is possessed by all living 

 nature, and is, indeed, the fundamental characteristic by which 

 living beings, animals and plants, are distinguished from lifeless. 

 Regarding the nature of excitability, Brown, like all other physi- 

 ologists of the time, had little to say. 



The hopes of the iatromechanics and iatrochemists of being able 

 completely to resolve vital phenomena into physics and chemistry 

 were not fulfilled. In irritability there existed a phenomenon 

 which, as was believed, distinguished all organisms from lifeless 

 bodies, and appeared to mock at a physico-chemical explanation. 

 The unexplained conception of irritability, therefore, in union with 

 the dynamical systems of Hoffmann and Stahl still prevailing, 

 became the starting-point of vitalism or the doctrine of vital force, 

 which in its most complete form asserted a distinct dualism of 

 living and lifeless nature. This tneory appeared first in France, 

 especially in the School of Montpellier, and later in Germany, and 

 its hazy notions of vital force soon controlled all physiology. In 

 France vitalism was founded by Bordeu (1722-1766), developed 

 further by Barthez (1734-1806) and Chaussier (1746-1828), 

 and formulated most distinctly by Louis Dumas (1765-1813). 

 The vitalists soon laid aside more or less completely mechanical 

 and chemical explanations of vital phenomena, and introduced, as 

 an explanatory principle, an all-controlling, unknown and in- 

 scrutable "force hyper me'chanique." While chemical and physical 

 forces are responsible for all phenomena in lifeless bodies, in living 

 organisms this special force induces and rules all vital actions. In 

 Germany vitalism did riot reach this degree of clearness. Its 

 founder, Reil (1759-1813), differed from the French vitalists, and 

 in his treatise " Ueber die Lebenskraft " expressed fairly clearly the 

 view that the phenomena of living organisms are chemico-physical 

 in nature, but that principles are at the same time in control which 

 are conditioned exclusively in organisms by the characteristic form 

 and composition of living substance. Later vitalists, however, 

 attempted no analysis of vital force ; they employed it in a wholly 

 mystical form as a convenient explanation of all sorts of vital phe- 



