The HPS TORY “of I'N. sac. 7's. 49 
with a defcription of the nature of the fand or 
ravel which are found in thofe parts. 
The falival veffels, Tab. XX XIX. Fig. vit. a. 
are two channels, clofed at their ends, They 
are of a membranaceous tranfparent fubftance, 
and are feated in the thorax, where they make 
a great many windings and turnings. In colour 
they refemble frefh curds, on account of their 
contents which appear through them; and ac- 
cordingly, on their being cut, nothing freely 
flows from them, the matter they contain being 
quite coagulated. The falival veffels unite at 
laft, fo as to form only one, 6, which terminates 
at the mouth, to which it is inferted upon in the 
back part of it. Near this infertion appear two 
{mall particles, ¢c, which very much refemble 
little mufcles. As I never met with any fluid 
matter in the veffels I have been laft defcribing, 
I cannot take upon me to fay ary thing pofi- 
tively, concerning the ufe which the Worm may 
make of them, though I called them falival vef- 
felves, becaufe fuch channels are very remarkable 
in other Worms, and alfo in nails. They ap- 
pear even in the Nymph of the Worm now be- 
fore us, and afterwards in the Fly, in which 
they are ftretched out to their full length, and 
after pervading the thorax, they terminate in the 
abdomen, being remarkably broad at their ex- 
tremities, if compared with their condition, as 
they were in the original Worms, this makes 
me believe, that thefe veffels do really, at laft, 
perform in the Fly, the office of falival duéts. 
The mouth, Fig, vir. d, at the bottom of which 
thofe falival ducts terminate, is here reprefented 
without the eyes, becaufe, in diflecting this 
Worm, both the eyes, and thofe parts which 
conftitute the fides of the head, very eafily fe- 
parate from the mouth. 
There is no part of this Worm without its 
pulmonary tubes *. They confift of two very 
confpicuous and confiderable tubes, Tab, XL. 
Fig.1.@a@, which are compofed, as it were, of flat- 
tifh rings, and aremuch wider in the middle 
than at the back or fore extremity, which runs 
towards the tail. ‘Thefe tubes are feated on the 
fides of the infect’s body, where they unite with 
the punéta refpiratoria, or breathing holes. It is 
probable, however, that the infect does not make 
ufe of them for breathing, till it is arrived at the 
Fly-ftate, when it lives in the air; fo that thefe 
channels remain clofed, till the infect comes to 
live in another manner, juft as the afpera arteria 
of a fcetus continues clofed, as long as it lies in 
the amnion, and furrounding waters. The pul- 
monary tubes are diftributed all over the body; 
they even penetrate the bowels, brains and nerves, 
in order to fupply every part witha this vivifying 
fluid. Great multitudes of them are to be feen 
in the fame place with the optic nerves, and the 
increafing membranes of the eyes, 4, and they 
gradually enlarge, in order to contribute to the 
formation of eyes in the Nymph, and afterwards 
anfwer all the purpofes of {uch parts in the Fly. 
Here and there thefe tubes meet, and unite toge- 
ther from the parts, cc, efpecially about the fides 
of the body, dddddd, where one may per- 
ceive a general anaftomofis of them one with 
another, by means of their common intermedi- 
ate branches, ftretching from one breathing hole 
to another 5 from hence {pring an infinite num- 
ber of ramifications, adminiftering to the memi- 
branes and mufcles of the fkin, which I here 
mark with points, eeee, and likewile to the in- 
ternal parts, At laft, the principal channels end 
at the feet, f; by two diftiné&t tubes opening into 
one paflage, where they ferve to take in air for 
the creature’s ufe, and alternately expel it, as has 
been already fhewn in the external furvey of that 
part, as the faid tubes appear very plainly through 
the tranfparent {kin of the infect. 
The largeft of thefe pulmonary tubes are fuf- 
ficiently confpicuous ; and they are compofed of 
crooked rings, and are alfo fomewhat flat, as I 
already mentioned, Tab. XL. Fig. 11. aa. On 
ftretching a piece of thefe tubes, thofe rings 
which compofe them, feparate very readily, fo 
as to roll out to the length of two or three {pans, 
and then they look very pretty, being like an ex- 
tended fcrew, or an untwifted fpiral, or a filver 
wire that had been wound up upon a needle, 4. 
This filver-like thread, of which the rings are 
formed, is almoft as {trong as the thread {pun by 
the Silkworm, on breaking, it fnaps with a 
crack that is very perceptible. 
The fat, Fig. rir. a, is diftributed all over the 
Worm’s body, fo as to be met with in the head, 
as well as in the abdomen and thorax. It is as 
white as the pureft fnow, except at the tail, 
where it generally inclines to bea little green, As 
to its textute, I don’t well know how to defcribe 
it, on account of the ftrange variety, in point of 
configuration of the particles that compofe it; 
for they are round, 4, oblong, ¢, broad, d, angu- 
lar, e, pyriform, or in the fhape of a pear, ff 
aid of almoft every other imaginable fhape. This 
fat is moft firmly united with the pulmonary 
tubes that run through it, g; fothat I believe it 
ferves, in the fame manner with the Omentum 
or Cawl in man, to bind together the blood-vef- 
fels, and convey them in fafety to their feveral 
deftinations. This fat, if laid on a piece of glafs, 
and held to a candle, melts like oil, and imme- 
diately flames ; this proves, that it is really what 
I have called it. Thefe particles, in regard to 
the veffels contained in them, might be called 
vafa adipofa, or fat veflels; but fuch a name 
would be improper for them. This fat in the 
Nymph and Fly, retains nothing of its original 
form, as may be feen by examining it in the 
Worm where it exhibits fo entertaining a fight, that 
it is impoffible for words to give a juft idea of it. 
Not only the form of the heart, Fig. rv. a. 
in this Worm, but its pulfations alfo may be 
feen through the fkin, under the third ring, 
counting from the head; but this is a great 
deal more perceptible in the Nymph, when 
* The number of thefe pulmonary veffels in the generality of infects is aftonifhing, and it is fo alfo in plants. They not only ap- 
peur confpicuous in all parts of them, but the greater part of the ftalk in May is compofed of them; this is particularly obfervable in 
the ftalks of bulbous plants: and in the fame manner we {ee it in the infe&t-tribe mot plain, and the tubes moft numerous, and di. 
vided in the fofteft {pecies. 
5 
iN {tripped 
