INTERNAL ANATOMY OF INSECTS. 175 
I. The muscles of insects may be considered in gene- 
ral as to their Origin ; Substance and Parts ,• Shape ,• Co- 
lour ; Kinds ; Attachment ,• and Motions. 
i. Origin. The origin of the muscular fibre in the 
higher animals is from the blood, the globules of which, 
by their coagulation in a series, appear to form it a ; and 
in insects it is derived from the same universal source of 
nutrition and accretion, but not till it has been concreted 
into the adipose tissue or epiploon before noticed 5 . In 
the pupa of the cabbage-butterfly, Herold observed that 
this substance first assumed a fine flocky appearance and 
a blue-green colour, and that from it so changed were 
produced tender bundles of muscular fibres, extending 
in various directions, the epiploon itself decreasing in 
proportion as they were formed c . 
ii. Substance and Parts. The muscular fibre in ver- 
tebrate animals appears to consist of globules arranged 
in a series, and of no larger diameter than those of the 
blood, — the mean diameter of which in the human sub- 
ject, when measured under the microscope by a micro- 
meter, is found to be about j^j^th part of an inch d . When 
Cuvier published his immortal work in 1805, the powers 
of any magnifier then constructed were not sufficient to 
enable this great physiologist to arrive at the simple 
fibre e ; but Mr. Bauer, by the use of improved glasses, 
amongst other discoveries that will immortalize his name, 
was the first to detect, under the directions of Sir E. 
Home, the ultimate thread of which the muscular bun- 
dles are composed f . Chemists distinguish the substance 
a Phitos. Trans. 1818. 174. /. viii./. 4—6. 
b See above, p. 150 — . l Schmctterl. 105. 
« Pkilos. Trans. 1819. 172, 174, 187. e Anat. Comp. i. 90. 
' Fhi/os. Trans. 1819. 1/5. 
