20 LABORATORY STUDIES IN ZOOLOGY 



systems of the body is received by the right auricle and passed 

 on to the ventricle. The left auricle receives blood coming 

 from the lungs and passes it on to the ventricle. 



2. The thick-walled ventricle is caudad of the auricles; it is 

 conical in form, with the apex pointing caudad. 



3. The truncus arteriosus is a tube arising from the right 

 cephalic border of the ventricle and extending obliquely cephalad 

 across the auricles. This trunk is the only course followed by the 

 blood upon leaving the heart for the several regions of the body. 



4. Lift up the ventricle and turn its apex cephalad. Do this 

 very gently and do not allow too much strain to come upon the 

 parts disturbed. Note three large vessels (veins) converging 

 in their course toward the dorsal side of the heart. The thin- 

 walled compartment which all three veins enter is the si7ms 

 ve7iosus or receiving station for the blood coursing back to the 

 heart from the body where it has performed its work. The sinus 

 venosus communicates with the right auricle which is the final 

 division receiving blood from the various systems of organs. 



On the plate showing the diagram of the heart label the parts. 



The Abdominal Viscera. — The liver is a large reddish-brown 

 organ behind and at the sides of the heart. It is either trilobed 

 or bilobed with the much larger left lobe further subdivided into 

 two parts. The lungs are two thin-walled but elastic sacs at 

 the sides of the heart; they He dorsad of the Uver and are often 

 concealed by it when viewed from the ventral side. The glottis, 

 noted in the study of the floor of the mouth, is the opening from 

 the mouth cavity into the larynx communicating with the lungs. 



Study the location and relations of the reproductive organs. 

 If your specimen is a female the ovaries will be seen as two large 

 bodies of irregular shape, each comprising a mass of spherical 

 black and white eggs, appearing like small shot. When fully 

 developed the eggs break through the walls of the ovaries into 

 the body cavity and find their way in a cephalic direction to the 

 openings of the paired oviducts. These are two long very much 

 convoluted tubes with thick white walls, lying at the sides of the 

 body cavity. After the relations of ovaries and oviducts have 

 been noted those of the left side may be removed. 



Turn the liver forward and note the stomach concealed by the 

 left lobe. Pass the handle of a needle through the mouth and 

 down the esophagus into the stomach which is an enlarged 

 portion of the alimentary canal between the esophagus and 



