INTERNAL ANATOMY OF INSECTS. 103 
analogous to what Ramdohr calls the thick intestine, 
though in these cases he regards it as an appendage of 
the rectum?. : 
I must now call your attention to the dile-vessels of in- 
sects. These, by Malpighi® and the earlier physiologists, 
who regarded them as a kind of lacteals, were denomi- 
nated varicose vessels: but Cuvier—and his opinion after 
some hesitation has been adopted by Ramdohr—consi- 
ders them as vessels for the secretion of dz/e, and as ana- 
logous to the diver of animals that have a circulation‘. 
As the want of blood-vessels prevents insects from hav- 
ing any gland, the bile is produced with them, as all 
their other secretions, by slender vessels that float in 
their nutritive fluid, and from thence secrete the elements 
proper to form that important product, which usually 
tinges them with its own yellow hue; though in the La- 
mellicorns and Capricorns they are of an opaque white, 
and in the Dytisci of a deep brown colour’. Their bitter 
taste further proves that they contain the bile*. They are 
long, slender, filiform, tortuous or convoluted, and mostly 
simple vessels ; sometimes gradually smaller toward the 
base‘, at others, towards the apex. In some, screw- 
shaped": in one larva, with hemispherical elevations? : 
in the cockchafer, part of them are fringed on each side 
with an infinity of short, blind, minute, setiform tubes, 
while the rest are naked*; they are composed of a single, 
thin, transparent membrane, according to Ramdohr'!; but 
* Tbid. 40. &’ De Bombyc. 18—. © Anat. Comp. iv. 153. 
a Jbid. = ford: 
£ Ramdohr 43. Cicindela campestris, t. iil. f. 1. K. 
® Phryganea grandis, Ibid. t. xvi. f. 2. h Notonecta glauca, 
Ibid. t. xxiii. f. 5. 1 Of Musca vomitoria, Ibid. t. xix. f. 5. 
® Tbid. taf. and G, f. 2. 1 Teid. 50. 
