On muscular Motion, > lis 



stances of ruptured tendo achillis, and fractured patella. 

 Instances have, however, occurred, wherein the fleshy bel- 

 lies of muscles have been lacerated by spasmodic actions ; 

 as in tetanus the recti abdominis have been torn asunder, 

 and the gastrocnemii in cramps j but in those examples it 

 seems that either the antagonists produce the eftect, or the 

 over-excited parts tear the less excited in the same muscle. 

 From whence it may be inferred, that the attraction of co- 

 hesion in the matter of muscle is considerably greater during 

 the act of coniracting, than during the passive state of tone, 

 or irritable quiescence; a fact which has been always as- 

 sumed by anatomists from the determinate forces which 

 muscles exert. 



The muscular parts of different classes of animals vary in 

 colour and texture, and not unfrequently those variations 

 occur in the same individual. 



The muscles of fishes and vermes are often colourless, 

 those of the mammalia and birds being always red : the 

 amphibia, the accipenser, and squalus genera, have fre- 

 quently both red and colourless muscles in the same animal. 

 Some birds, as the black game*, have the external pec- 

 toral muscles of a deep red colour, whilst the internal are 

 pale. 



In texture, the fasciculi vary in thickness ; and the reti- 

 cular membrane is in some parts coarse, and in others de- 

 licate : the heart is always compacted together by a delicate 

 reticular membrane, and the external glutasi by a coarser 

 species. 



An example of the origin of muscle is prf^sented in the 

 history of the incubated egg; but whether the rudiments 

 of the punctum saliens be part of the cicatricula organized 

 by the parent, or a structure resulting from the first process 

 of incubation, may be doubtful : the little evidence to be 

 obtained on this point seems in favour of the former opi- 

 nion ; a regular confirmation of which would improve the 

 knowledge of animal generation by showing that it is gem- 

 miferous. There arc sufficient analogies of this kind in 

 nature, if reasoning from analogies were proper for the 

 present occasion. 



The punctum saliens, during its first actions, is not en- 

 eompasscd by any fibres discoverable with microscopes, 

 and the vascular system is not then evolved, the blood 

 flowing forwards and backwards, in the same vessels. The 

 coinmenccjnent of life in animals of complex structure is, 



• Tetrao tctrit. Lino- 



H 3 from 



