274 SOLID PARTS OF ANIMALS. 



fibres about ^o th of an inch in diameter, and surrounded by cir- 

 cular striaB varying in thickness and in number. Each fibre is 

 divided into bands or fibrillae composed of many ultimate fila- 

 ments. Each fibrilla is divided into filaments, of which every 

 fibre of ^o th of an inch diameter contains about 100. The dia- 

 meter of the filaments is about one-third the size of the globules 

 of the blood. 



Muscles, while they retain their vitality, contract when stimu- 

 lated either by the prick of any sharp instrument, or by the ap- 

 plication of any acrid or stimulating substance. When they lose 

 this property they are considered as dead. Sir Anthony Car- 

 lisle has shown that a muscle is stronger while it retains its irri- 

 tability, than when it has lost that property. He laid bare the 

 muscles of the two hind thighs of a frog, and removed the femoral 

 bone. He then attached weights to each set of muscles till it 

 was ruptured. The experiment was made upon the muscles of 

 one leg while they retained their irritability, and upon the mus- 

 cles of the other leg, after the irritability was gone. The mus- 

 cles retaining their irritability were ruptured by a weight of 

 six pounds avoirdupois ; those that had lost it by a weight of five 

 pounds.* 



Through the muscular fibres run a great number of blood- 

 vessels and nerves. These may be removed to a certain extent, 

 but not completely. Especially the nerves, which are very nu- 

 merous, and which become at last transparent and invisible with- 

 out any sensible termination ; the cellular substance also which 

 surrounds the muscular fibres, and divides them into bundles, is 

 a substance of quite a different nature from the muscular fibre 

 itself, and would require to be removed before the chemical na- 

 ture of that fibre could be accurately determined. The red co- 

 lour of the muscle is doubtless owing to the existence in it, of a 

 vast number of capillary vessels filled with red blood. 



The first attempt at a chemical examination of the muscles of 

 animals was by M. Claude-Joseph Geoffroy, Junior, in 1730.f 

 He examined the flesh of oxen, calves, sheep, fowls, pigeons, 

 pheasants, partridges, in order to determine how much of each 

 was soluble in water by boiling, and how much each lost when 

 dried over the steam-bath. The subject was farther continued 



* Ptril. Trans. 1805, p. 3. 



f Memoires de 1' Academic des Sciences, 1730, p. 217, 



