Lab. -8-
The frog
Practical Biology
The frogs are consider from the amphibians in order Anura (meaning tail-less)
living on land and in water.
* General morphology for frog:
1- The hind limb longer than forelimb.
2- Absence of neck and tail
3- Up and down movement of the floor of the buccal cavity (a respiratory
movement).
4- The external nares or nostrils, which two small openings lying near the anterior tip
of the head.
5- The eyes are bulging, which are surrounded by two eyelids and nictitating
membrane.
6- The tympanic membrane or ear-drum, which is a more or less circular area found
posterior to each eye.
7- Frogs have a long, sticky tongue which they use to capture food.
8- Maxillary teeth: teeth found on the maxillary bone or upper jaw.
9- Vomerine teeth: two knob-like, located on the upper jaw of the frog.( (The
vomarine and maxillary teeth are used for holding the prey).
10- frog's external structures also include the webbed feet and the cloaca opening.
* Frog's skin is soft, smooth and loose. It is always kept moist and slimy by mucus
secreted by cutaneous glands. therefore, frog's skin serves as an important accessory
respiratory organ. Being slimy, it also helps the frog in slipping out of the grip of an
enemy.
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*Dissection the frog
* Dissection is a fine process which requires certain instruments:
1- Scalpels
2- Scissors: two, a fine pointed pair for dissecting delicate tissues, and another strong
pair for cutting bones.
3- Two forceps: one pair pointed, the other blunt.
4- Pins and small nails.
*Note: keep the dissecting instruments in special case and clean after
every dissection.
* Anesthesia methods in frogs:
There are three methods using for anesthesia in frog:
1- The knocking: it is knocking a frog is by holding it by it is hind-limbs and
striking it violently against edge of table.
2- The pithing: it is mean paralyzes of animal completely by separate spinal cord
about central nervous system or brain by using the dissecting needle.
3- The anaesthetizing: by putting the animal in a small tin with a piece of
cotton wool rinsed in chloroform or ether.
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