30 THE FROG 



163. rami intercommunicantes with the spinal nerves. 



164. The splanchnic nerve runs along the coeliaco- 

 mesenteric artery (61) and receives branches from 

 the third, fourth, fifth, and sixth sympathetic ganglia, 

 which unite with each other to form the solar plexus. 



Drawing 14. Draw the ventral surface of the dorsal 

 body wa*n, labeling all the structures you have just 

 identified (x2). 



Place the frog dorsal side uppermost. Make a transverse 

 incision in the skin across the head just cephalad of the 

 arms, strip the skin forivard, and note: 



165. The slender columella is in the aperture lying be- 

 neath the tympanum (6). Note its relation to the 

 tympanum. 



166. There is a tympanic cavity (middle ear). 



Carefully remove an eyeball, by cutting through the eyelids, 

 the muscles of the eyeball, and the optic nerve {193). Cut 

 the eye into two portions, by cutting across it with scissors 

 to one side of the pupil in any except the sagittal (vertical 

 longitudinal) plane. Place the larger portion in a dish of 

 water and note the following structures. 



167. The transparent cornea at the external (exposed) 

 surface above the iris, continues into 



168. the inner opaque sclerotic layer. 



169. The thin black pigmented chorioid layer extends 

 outward under the cornea as the iris (3). 



170. A thin, yellow-white layer at the proximal half of 

 the eye is the sensory retina. 



171. The crystalline lens is a large solid body which is 

 transparent in a fresh specimen. 



Drawing 15. Make a diagram of the eye on the basis 

 of this dissection (x2). 



