A MANUAL OF ZOOLOGY 73 



Find the opening from it into the large intestine. Find 

 the opening into the urinary bladder ventral to this. In 

 a female specimen the openings into the oviducts will be 

 found in the top of eminences on each side. In male 

 specimens slits in the same relative position mark the 

 openings oy;he vas deferens. Put bristles Into them and" 

 trace them^ack to the testes which lie a short distance 

 in front of the pelvis. Attached to each of the testes is a 

 dark colored mass, the epididymis. Attached to the inner 

 ventral side of the cloaca is to be found the external gener- 

 ative organs of the male. Along its dorsal border is a deep 

 groove, the uretliral groove. Make a diagrammatic sketch 

 of the digestive, the urinary, and the reproductive systems, 

 showing the general form and relations. Near the junc- 

 tion of the small and the large intestine find the small round- 

 ish spleen suspended in the mesentery. Underneath the 

 posterior end of the lungs on each side of the median 

 line find' the lobulated kidneys. Trace the ureters leading 

 from their ventral surface. Do they lead into the bladder? 

 Pull out the head and notice the large muscles at- 

 tached to it. Find their origins and insertions. Cut them 

 from their attachments to the head. Note the manner in 

 which the neck is bent if the animal was killed with the 

 head retracted. How would the muscles act in> order to 

 protrude or retract it? Break the spinal column as far 

 back as it is free. Cut all attachments and remove the 

 head. Posterior to the angles of the mouth you will find 

 th« tympanic membranes. How do they compare with 

 those of the frog? Remove the skin over them. Notice 

 the white cartilaginous ring inclosing- a round opening 

 over which is stretched a cartilage-like membrane which 

 seems to be more dense in the middle and membranous 

 at the edges where it attaches to the white ring. Cut 

 around the inside of the ring so as to free the tympanum. 

 Pull up one edge of it and notice a slender column leading 

 from it back into the ear cavity. The column and its outer 

 expanded tympanic part are together called the columella. 

 At the lower edge of' the cavity will _be found the very 

 narrow eustachian tube leading to the back part of the side 

 mouth cavity. Demonstrate this by Vrorking both from the 

 mouth and thenar side. Follow carefully the columella, 



