A MANUAL" OF ZOOLOGY 17 



crop. What does the crop contain? MaKeta draKjng-Of 

 some of the contents nnder^the microscppe'. Just posterior 

 to the crop-wtrPBe found the gizzard. Compare with the 

 crop. Leading from the gizzard will be found the stomach- 

 intestine. The yellowish mass of cells on the dorsal sur- 

 face of the intestine were formerly supposed to have the 

 function of a pancreas, but now they are supposed to be 

 connected with the process of excretion. Cut through the 

 intestine a little to onje side of dorsal line and find a 

 longitudinal fold, the typhlosole. Examine the contents of 

 the intestine in the posterior region with the microscope, 

 and compare with that of the crop. Make_aa_piitline draw- 

 ing of jth^bfldy^Ji^aid oEen_onjtlie_miii:3to'sal line and locate 

 carefully all parts of the digestiye_ apjgaratus .in__thelr. 

 proper segment or segments. 



Carefully clean a live specimen and look for circula- 

 tory system. The dorsal blood Vessel may be seen as a red 

 line under dorsal surface. Carefully watch for pulsations 

 jn this vessel. By killing a specimen in alcohol the fol- 

 lowing vessels may be worked out under favorable condi- 

 tions (the name will give the location): the circum-oesoph- 

 ageai blood vessel; the supra-neurai blood vessel; the 

 lateral oesophageal blood vessel. By the use of two pairs 

 of fine-pointed forceps, a portion of a blood vessel may be 

 removed without the blood getting out. Place this under 

 the microscope and study the blood. What is its color? 

 Are there corpuscles? JCow do they, compare with those 

 of the body cavity? Account for the color of the blood. 

 Does it coagulate upon exposure? 



To study the nervous system, remove the alimentary 

 canal, from the pharynx back. Dorsal to the oesophagus 

 the supra-oesophageal ganglia will be found. Leading ven- 

 trally from these ganglia on either side of the oesophagus, 

 white threads, circum-oesophageal commissures, may be 

 found, joiniiig-the ventral nerve cord. What is the extent 

 of the ventral nerve cord? Look for ganglia on the ven- 

 tral nerve cord." Wh^jt is the relation of the ganglia to 

 the segments of the body? Make a, diagran^of jthe_nervous 

 system. 



