290 The Older Doctrines [lect. 



problems, assumed, being led to do so by reasons of analogy, 

 without attempting to make any direct observations on the 

 matter, that a muscle during contraction was inflated, that 

 it suffered increase in bulk. Now Borelli took this view 

 although as we have seen he had freed himself from the 

 old, and to a large extent still current grosser conceptions of 

 the nature of the animal spirits. To those who held these 

 grosser conceptions the increase in bulk of a muscle during its 

 contraction was a natural and indeed necessary postulate ; the 

 animal spirits flowed into the muscle and made it swell up. 

 Such, with the admixture of certain new chemical conceptions, 

 was as we have seen the teaching of Willis. 



All such ideas Glisson confronted with a single experiment, 

 the result of which deprived them of all solid basis. He gave, 

 and he was the first to give, the exact proof that when a 

 muscle contracts it does not increase in bulk ; and his old 

 experiment still stands in substance as the proof given in our 

 modern text-books. In his work De Ventriculo he says, 



" But indeed this explosion and inflation of spirits has now 

 " for some time past been silenced, convicted by the following 

 " experiment. Take an oblong glass tube of suitable capacity 

 "and shape. Fit into the top of its side near its mouth 

 ** another small tube like a funnel. Let a strong muscular man 

 "insert into the mouth of the larger tube the whole of his 

 w bared arm, and secure the mouth of the tube all round to the 

 " humerus with bandages so that no water can escape from the 

 "tube. Then pour water through the funnel until the whole 

 " of the larger tube is completely filled, and some water rises 

 "up into the funnel. This being done, now tell the man 

 "alternately to contract powerfully and to relax the muscles 

 "of his arm. It will be seen that when the muscles are 

 "contracted the water in the tube of the funnel sinks, rising 

 " again when relaxation takes place. From which it is clear 

 " that muscles are not inflated or swollen at the time that they 

 " are contracting, but on the contrary are lessened, shrunk, and 

 " subsided. For if they were inflated the water in the tubule 

 "so far from sinking would rise. From this therefore we may 

 " infer that the fibres are shortened by an intrinsic vital move- 



