22 



PHYSIOLOGY 



CHAP. 



results were contradictory. Many observers were unable to dis- 

 cover any variation in the volume of the muscle, while others saw 

 a more or less marked diminution in volume during tetanus. 



Among the former we must 

 mention Barzellotti (1795-96), 

 who invented the method of 

 introducing the muscles of a 

 frog into a closed vessel full of 

 water, which carried a capillary 

 tube: among the latter, Erman 

 (1812), who with the same 

 method observed a marked 

 diminution in volume. An 



brane, pulled out by a spiral spring. A metal , , . , -, 



button in the centre of the membrane carries the exnaUSllVe research Dy 



FIG. 14. Myograph suitable for man, to record 

 increased bulk of the muscles. (Marey.) Con- 

 sists of a capsule covered with a rubber mem- 



exciting current to the skin immediately above /-i oq^\ 

 the muscle to be explored. The compression of V.- 1 - 00 ' )> 

 the air in the capsule during the contraction is lotti's method With nice ad- 

 recording tambour. ' justments, also failed to obtain 



even minimal variations of 

 volume in a muscle during tetanisation. 



The muscle therefore changes in form and extent of surface, 

 but not in density and volume, during activity. Were they not 

 sanctioned ]py use it would be better to give up the inappropriate 

 expressions " contraction " and " relaxation," to indicate the two 

 phases of muscular activity. 



The state of contraction in a muscle can also be studied by 

 tracings of the area of its cross-section. Marey invented special 

 myographs for this purpose which can be applied to man in 

 physiological and clinical research. The simplest of these are 

 shown in Figs. 14 and 15. Curves of simple contraction and of 



Fio. 15. Exploring tambour that can be used as a myograph to transmit the phases of increasing 

 thickness of a contracting muscle to a tambour with writing lever. 



tetanus recorded by this method closely resemble those we have 

 already analysed in the corresponding changes in the length of a 

 muscle. But there is one important difference ; while the former 

 record the algebraic sum of the changes in length in all the 

 different parts of the muscle, the latter only trace the changes in 



