C. HISTOLOGY. 



I. EPITHELIUM. 



a. Columnar epithelium : Gently scrape the inner surface of a 

 frog's intestine that has been preserved in Miiller's fluid. The frag- 

 ments removed, under a high power, are seen to be composed of 

 elongated cells each with a nucleus and having one end more pointed 

 than the other. 



b. Ciliated epithelium: Cut off a bit of the mucous membrane 

 from the tongue or roof of the mouth of a freshly killed frog, mount 

 in physiological salt solution and examine under a high power. Xote 

 the appearance on the edge due to the cilia, as the cilia become less 

 active individual ones can be distinguished. Scrape off some of the 

 epithelium and examine under a high power in physiological salt 

 solution ; note the shape of the individual cells and the group of 

 cilia at one end. Draw both kinds of epithelium. 



II. MUSCLE. 



a. Tease out a bit of injected frog's muscle preserved in alcohol, 

 (i) It is composed of elongated fibres, some of which may be split 

 up somewhat into fibrillae. (2) Numerous blood capillaries are 

 found amongst the fibres. 



b. Examine with a high power: (i) Each fibre shows alternate 

 darker and lighter bands. (2) A delicate sarcolemma or structure- 

 less membrane envelops each fibre and can be easily seen at places 

 that are broken or twisted. 



c. Tease out fresh muscle in salt solution and examine with high 

 power to note the above points ; treat with acetic acid and observe 

 the oval nuclei in the fibre. Drazv. 



III. NERVE. 



a. Nerve fibres: Tease out a bit of fresh nerve in salt solution 

 and examine with a high power. Note: (i) \Yell defined fibres, 

 each with a double contour, together with white fibrous tissue make 

 up the mass of the nerve. (2) Each fibre has a highly refractive 

 border (medullary sheath) and a central homogeneous a.vis cylin- 

 der, well seen in torn specimens where also the very delicate, outer- 

 most membrane (primitive sheath), may be some times made out. 



b. Ganglion cells : Examine prepared specimens of ganglion cells 

 that have been stained to make out the structure of the cells. Draw 

 a nerve fibre and a ganglion cell. 



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