110 The BiOvOds 8 NA TU Rie oy 
larly furrounds, being very clammy and glu- 
tinous. For this reafon the eggs do not pafs 
faft, or eafy thro’ the tubes, but very leifurely, 
and by flow degrees, and chiefly by the action 
of the mufcular fibres adminiftring to the tubes, 
which little by little pufh the egg and its nou- 
rifhment into the uterus. 
I find this white of eggs to be a very nou- 
rifhing fubftance ; for which reafon, when I 
had young Frogs to rear, I ufed, as often as I 
wanted, other food that was proper for them, 
to take a tube from the body of a female Frog, 
and give it to them cut into pieces, which they 
immediately faftened upon, fucking eagerly the 
. juices that flowed from thence. ‘This matter 
even diffolves, and diffufes itfelf in water, like 
the white of the Frog’s egg, being of a fimi- 
lar compofition and fubftance: hence the tube 
itfelf, on being juft thrown into water, be- 
comes by degrees eight times as thick as be- 
fore: but this experiment muft be made within 
a few weeks of the eggs pafling thro’ the tubes, 
as afterwards they contain no more of the white 
or albumen. 
This tube, no doubt, is furnithed with its 
glands ; tho’ as yet I have not had the fatisfac- 
tion of feeing them diftin@ly. I obferved, how- 
ever, that the tube on its infide is thoroughly 
lined with. a regular reticulated glandulous 
coat; from whofe pores the albumen, or white 
is fecreted. Behold what, and how many 
wonders appear in the Frog only! But we 
ought not to content ourfelves with a fingle 
experiment ; we ought to try every thing that 
appears, and in every manner in which it can 
be tried, to acquire a perfect knowledge of any 
_ thing we defire to be thoroughly acquainted 
with. 
It is no eafy matter to determine whether 
the uterus contributes alfo to the generation of 
the white of the egg, and the full perfection 
of the egg itfelf, or only ferves to collect all the 
eggs, and eject them at one and the fame time. 
To me it appears probable, that the uterus 
ferves merely as a receptacle for the eggs. It 
differs greatly from the tubes, as it is mem- 
branaceous, and in part fibrous, or compofed 
of, or furnifhed with many fibres ; but it 1s no 
ways glandular, for which reafon it 1s always 
found in a contracted ftate, and never exhibits 
itfelf diftin@ly, but when naturally diftended 
with eggs, blown up vith air, or injected with 
fome kind of liquid. It is even impoffible to 
diftend it by macerating it in water; fo that 
upon the whole,; no two things can be more 
different than the tube and the uterus. 
The eggs, as I faid before, at the time that 
the Frog is to difcharge them, break loofe from 
the lobules of the ovary, to the infides of which 
they adhered, and are forced by I know not 
what motion thro’ the cavity of the abdomen 
into the open mouths of the tubes ; but I can- 
not exactly determine how much time may be 
requifite for this paffage, as the Frog is very 
far from being tran{parent like fome other 
animals. It may not, perhaps, be impoflible to 
obferve this procefs in fome other {pecies : ne- 
I 
verthelefs, the knowledge of this truth could 
then be only analogically obtained. 
About the fame time we find that the tefti- 
cles and {permatic veffels in the male Frog Ail 
with fperm. Thefe animals become then {fo 
eagerly intent on the bufinefs of propagation, 
that they take no care in a manner of their 
own fafety ; fo that they may be eafily caught 
with the hand. I believe that they eat no- 
thing, or very little, during this fit of luff, which’ 
Jafts more or lefs time, according to the heat 
of the weather. ; 
To carry on the intercourfe of the fexes, 
which this great work requires, the male 
Frog leaps upon the female, and when feated 
on her back, he faftens himfelf to her very 
firmly.. For this reafon, the Dutch coun- 
try boors, with great propriety, tho’ in their 
vulgar way, call this manner of copulation, the 
riding feafon of the Frogs, as the male is car- 
ried about, riding, as it were, by the female. 
It is neceffary, thofe who intend to diflect this 
infect, fhould know how to diftinguith the male 
from the female. I have obferved two marks 
by which this diftin@tion may be made. Inthe 
firft place, the male has two air bladders, which 
he expands in croaking ; and the mouths of thefe 
bladders are feated on the fides of his jaws. 
Thefe bladders confift of two membranes, which 
may be eafily parted, and feparately diftended 
with air, and fo preferved. One of thefe mem- 
branes is a continuation of the external fkin; 
the other a continuation of the membrane of the 
palate; and this laft is furnifhed with blood vef- 
fels and mufcular fibres, which ferve to contract 
and dilate thefe bladders. Properly fpeaking, the 
orifices of thefe bladders lie in the upper region 
of the mouth, where the gums are feated in men ; 
and near them, within the mouth likewife, are 
to be feen the orifices of the organs of hearing,’ 
or of the animals ears. ‘The tympanum, or drum 
of the ear, lies withoutfide, immediately under 
the {kin. The fame conftru€tion obtains alfo in 
the Chameleon. 
The other mark of the male Frog is furnithed 
by the animal’s thumb, which is very thick in 
the males, Tab. XLVUH. Fig. vi. a. perfeGly 
black in fome kinds, and covered with a creat 
number of papillz, 4, which are likewife of an 
extreme blacknefs, and conftructed in the fame 
manner with the papillz on the tongues of oxen. 
Thefe papillae become rough in drying, and, like 
the rough {kin called fhagreen, feel very ruggid; 
their ufe I fhall prefently defcribe. 
The males, at the time of copulation, leap on 
the females, and they continue fometimes on their 
backs, for forty days fucceflively, according as 
the feafon of the year is more or lefs cold, and 
the eggs take up more or lefs time in their paf- 
fage to the organ that is tofhed them, Some- 
times thefe animals continue together in this man- 
ner even for a much longer time ; as when the fe- 
male is weak or fickly, and the eggs on that ac- 
count defcend more flowly through the tubes ta 
the uterus, or when they meet with delays in 
the abdomen or uterus, as I obferved in fome 
Frogs, whofe intercourfe lafted a very long time. 
The 
= Fees ; 
