THE FROG 17 
Pass a bristle into the anterior end of the oviduct. Posteriorly 
each oviduct passes into a thin-walled distensible portion, the 
uterus; this opens into the cloaca. How are the oviducts attached 
to the body wall? 
V. THE PERITONEUM. 
The space between the alimentary canal and the body wall is 
known as the celome, or body-cavity, and the thin membrane 
which lines the body cavity is the peritoneum. Near the mid- 
dorsal line the peritoneum is deeply infolded to surround the 
intestine, which lies within the edge of the fold. Between the in- 
testine and the dorsal body wall the two layers of the fold are 
in contact, forming the mesentery which serves to support the 
intestine and bind the several coils together. The abdominal 
viscera (intestine, etc.) are really outside of the peritoneum 
which forms a closed sac into which the viscera appear as if 
pushed from the outside. Observe the peritoneal covering of the 
pericardium, liver, gall-bladder, and the vertical mesentery 
(severed during the preliminary dissection) which unites the 
liver to the ventral body wall. The ovaries, testes and oviducts 
possess special mesenteries; examine them. The bladder is 
attached by a short mesentery to the ventral side of the rectum; 
notice the other mesenterial attachment of the bladder. The 
lungs project from in front into the body cavity and therefore 
possess a complete investment of peritoneum. The blood vessels 
of the viscera run within the mesenteries. The kidneys lie dorsal 
to the peritoneum, within the great lymph space between the 
peritoneum and the dorsal body wall. 
Study the course of the peritoneum in the diagram of a cross- 
section of the frog’s body shown on page 78 of Holmes’ Biology 
of the Frog. Make a similar diagram of a cross-section of the 
body of a female frog. (This diagram should be about 10 cm. in 
diameter.) If your specimen is a male, consult the model show- 
ing the internal organs of a female frog, also a preparation of 
the female reproductive system. 
VI. Tue DicestivE SYSTEM. 
A. General Anatomy.—Review your observations on the anat- 
omy of the digestive system and make an outline drawing (X 2) 
