190 



THE FROG— THE PLATANA 



(b) The hind-lirnb, consisting of thigh, shank or leg, and foot with elongated 

 ankle-region and five webbed digits, the shortest one being the hallux 

 or " great toe." [In the Platana the inner three digits have claws.] 



Name the parts of the limbs, and number the digits from within outwards. 



Mouth Cavity. 



Open the buccal or mouth cavity widely, and make a sketch showing : 



(a) The teeth on the upper jaw. 



(b) The teeth on the vomers. \There are no vomerine teeth in the Platana.] 



(c) The internal nares or internal openings of the nostrils. 



{d) The pair of Eustachian apertures, at the angles of the mouth. \In the 



Platana there is a single Eustachian aperture.] 

 {e) The tongue. [Absent in the Platana.] 

 (/) The glottis, the slit-like opening of the larynx which leads from the 



lungs. 

 ig) The gullet. 



Pass a seeker into the Eustachian aperture, along the Eustachian tube and 

 through the tympanic membrane. [In the Platana, owing to the compleadty of 

 the Eustachian tubes and the bony form of the ear, cavity, it is not possible to do 

 ihis.^^ 



-Teeth on Upper Jaw 



Vomerine teeth 



Internal nares Internal nares-. 



--Eustachian aperture 



^Gullet 



Gullet 



Glottis 



A B 



Fig. 65. — A. Buccal or Mouth Cavity of Rana ; and B. of Xenopus. 



Muscular System and Vascular System (part). 



1. Lay the Frog on its back under water in the dissecting-dish, and fix it 

 firmly by pins through the limbs. Using scissors, cut through the skin along 

 the middle line, the whole length of the body. Reflect the skin on each side 

 and pin it down, noticing its loose attachment and the subcutaneous lymph 

 spaces. Make a drawing showing : 



(a) The muscles. 



(i) Two pectoralis muscles, each consisting of two portions passing 

 to the upper arm ; one portion arising from the sternum, the 

 other from the outer side of the rectus abdominis muscle. 



