98 Beco7'ds of the Indian Museum. [Vol. XV, 



towards the solution of this problem that the present work was under- 

 taken. 



Material and Methods. 



' I have investigated in detail the structure of the middle ear of the 

 large Indian frog Rana tigrina, Daud.^ There are several forms 

 closely alhed to this frog in India, but the form common in Lahore 

 where the work was done is the typical one, as was ascertained by send- 

 ing some specimens to Dr. Boulenger in London. Besides a large num- 

 ber of dissections of this frog I cut sections of decalcified specimens 

 of both young and adult frogs ; these sections were found to be very 

 useful in clearing up the doubtful points and indicating the exact relation- 

 ships of the various parts. 



Through the kindness of Dr. N. Annandale, Director of the Zoological 

 Survey of India, Calcutta, I was able to examine the large collections 

 of frogs in the Indian Museum, Calcutta, and so am able to add an 

 account of the structure as it occurs in a large number of other Indian 

 frogs. I am also deeply indebted to Lt.-Col. J. Stephenson, D. Sc... 

 I. M.S., Professor of Zoology and Principal, Government College, Lahore, 

 for kindly giving me leave to go to Calcutta to work in the Indian 

 Museum, and for sanctioning a special grant towards the expenses. 



Rana tigrina. 



The structure of the middle ear in this frog will be described in the 

 following order : — 



(1) The tympanic area. 



(2) The tympanic membrane. 



(3) The tympanic cavity and associated skeletal structures. 



The Tym/panic area (fig. 1). — I have reluctantly changed the 

 widely accepted nomenclature in order to remove the existing con- 

 fusion, and have given the name of tympanic area {T. a.) to the area 

 of skin situated in the temporal patch on the side of the head. This 

 area is continuous with the skin, but is tightly stretched over the marginal 

 ring of the annulus tympanicus, and is slightly more depressed than the 

 skin all round it. It is nearly circular in outhne and is a little smaller 

 than the eye. About the middle of this structure the attachment of 

 the columella auris can be seen as a nodular protrusion. 



The histological structure of this portion of the skin is quite similar 

 to that of other parts of the skin, except that the number of cutaneous 

 glands is much smaller ; about the middle no cutaneous glands are to 

 be seen {text fig. 1). 



The Tympanic memhrane (figs. 2, 3, and 4). — This is quite a dis- 

 tinct structure lying immediately underneath the so-called tympanic 

 membrane of authors. It can be easily separated from the skin 

 covering it. On the skin being reflexed by a cut, the tympanic mem- 

 brane (T. m.) is seen to be of a rounded-oval form shghtly notched 

 at the upper side, and produced into a httle projection on its lower. 



1 I have satisfied myself by examination of specimens of R. esculenta and R. tem- 

 poraria that the structure in these frogs is also essentially similar to that of R. tigrina, 



