410 GLISSON. HALLER. WHYTT. [BOOK I. 



motion 1 . His opinion generally prevailed until the time of Haller, 

 whose doctrine of the independent irritability of muscle marks the next 

 advance in the theory of muscular contraction. The term Irritability 

 was not indeed new to Physiology. The name, and in a certain sense 

 the notion also, was introduced by Glisson in the latter half of the 

 seventeenth century. He taught that irritability was a property of 

 the elements of our bodies, even of the bones and juices, which was to 

 be attributed to a natural perception unaccompanied by any sensation 

 whatever. It was supposed to depend upon 'Archaeus who is the 

 framer of his own body' ; and it could be demonstrated after death by 

 the application of acid and pungent liquors 2 . Bat it was Haller who 

 first gave the idea a firm foundation in experiment. Resting on the 

 experiments of Haller and his pupils, this important doctrine was 

 definitely formulated in a Treatise on the Sensible and Irritable 

 parts of Animals 3 . Irritability was defined as the property, pos- 

 sessed by muscular fibres alone in the body, of shortening when 

 they are touched ; while those parts were called sensible which, 

 when handled, transmit the impression of the touch to the soul, or, 

 in animals, lead to evident signs of pain and disquiet. Irritability is 

 distinct from sensibility, since nerves, the most sensitive of structures, 

 -are absolutely^! e void of irritability. Stimuli applied to nerves, how- 

 ever, lead to convulsions and palpitations of neighbouring muscles, 

 but only in such as are directly supplied by the nerve stimulated. 

 Muscles contract after separation from the brain, after their nerves 

 are all cut away, and even after removal from the body. Hence 

 irritability is a property quit&^apart from the soul and the nerves. 

 Haller thought it probable that, ^me time or other, the use of the 

 nerves with regard to the muscles would be reduced to conveying to 

 them the commands of the soul, and to increasing and exciting that 

 natural tendency which the fibres have of themselves to contract 4 . 

 The property of producing motion is different from all other proper- 

 ties of bodies, and it probably resides in the glutinous mucus rather 

 than in the earthy parts of muscles. It is a property of muscles as 

 gravity is a property of matter generally, and it is doubtless owing 

 to a physical cause depending on the arrangement of ultimate parti- 

 cles. It is destroyed by drying the fibre, as well as by opium. 



^ The most active opponent of Haller in this country 



was Robert Whytt 5 , Professor of Medicine in the Univer- 



1 Georg. Ern. Stahlius, Theoria Medica Vera, 1708. Ed. Lud. Choulant. Lips., 1831. 

 Tom. i. sec. vi. p. 466. Georg Ernst StahVs Theorie der Heilkunde. Dargestellt von 

 Wendelin Ruf. Halle, 1802, p. 206. 



2 Francis Glisson, de Ventriculo et Intestinis, c. vii. Quoted by Haller, Op. cit., 

 infra. 



3 Haller, " de Partibus corporis humani sensilibus et irritabilibus." Commentarii 

 Soc. reg. Scientiarum Gotting. Tom. n. 1752, p. 114. A Dissertation on the Sensible 

 and Irritable parts of Animals. Translated from the Latin. London, 1755. 



4 Haller, Loc. cit., p. 139. 



6 Robert Whytt, Physiological Essays, Edinburgh, 1766. Third Edition. On the 

 Vital and other Involuntary Motions of Animals, Edinburgh, 1763, Second Edition. 



