378 PHYSIOLOGY, CHEMISTRY AND MORPHOLOGY 



nomena, if we allow that the physics and cheiiiistry iuvolved have 

 special characters of their own, and that they freqnently are meclian- 

 ical in their operations, and that the effects produced by them are of a 

 quite x)cculiar nature. 



It was in accordance with the natural development of human thought 

 that physiologists should iirst be led to examine the physical phe- 

 nomena of life, or to look to physics for explanations by analogy, and 

 that, in spite of the most serious objections, it was only later that they 

 took np the chemical side of bioh)gical (piestions, trying" to give a con- 

 cejition of them based upon the mechanism of atoms. In short, it may 

 be said that since that has been done many problems of physiology are 

 treated from the standpoint of chemistry, and that we resort to that 

 science for what many believe to be the latest intelligence concerning 

 the manifestations of life, 



A quite characteristic exami»le of the development of the general 

 ideas that controlled and still control physiology is found, among many 

 others, in the theory which attempts to account for a phenomenon of 

 great interest, and now nuich studied, that of inhibition. You know 

 that by inhibition Ave designate the arrest of a functional act induced 

 by an antagonistic act, but not, as in i)aralysis, by suppressing totally 

 or in part the conditions producing the phenomenon. We have a well- 

 known example of it in the action of the pneumogastric nerve npon 

 the heart. Whenever that nerve is excited by a sufHciently powerful 

 stimulant, the movements of the heart cease, returning again as soon 

 as the excitation is withdrawn or the force of the nerve exhausted. In 

 this case we have produced by means of an excitant a nervous vibra- 

 tion, which, elaborated in certain ganglia situated in the substance of 

 the heart, neutralizes the action of the excito-motor cells. This con- 

 clusive experiment, first made in 1840 by the brothers Weber,' enconn- 

 tered objections based, it nnist be confessed, upon a prejudice arising 

 from the systematic notions then in vogue. At that time physiology 

 was at a period of its history when, imbued by somewhat crude mate- 

 rial conceptions, it was alleged that everything could be simplilied so 

 as to reduce every movement to a retlex act. So it was denied tliat 

 there could be found in our organism any other than sensory and motor 

 fibers. 



We ought to add that the philosophical tendency of that time had 

 great force, for among those who refused to allow that the experiment 

 of Weber had any special importance were two of the most illustrious 

 names of modern physiology." But other acts of restraint were found 

 besides the inhibition of the heart, so that the opposition could no 

 longer be maintained, especially when it was found that in the nervous 

 centers themselves there occur inhibitory processes, in which, as we 



' E. H. Weber. " Ueber Eduard Weber's Entdeckungeu iu der Lebre von deu 

 Muskel-contractioii," Archiv fiir Auatomieuud Pbysiologie (Miiller's Arcbiv), Berliu, 

 184(), pa-o 4S3. 



'Schia, MolescU. Uuters., VI, page 201, 1859, aud VII, page 401, 1861. 



