DISSECTION 159 



apophyses ; but it is doubtful whether these really 

 belong to the same category as the appendages of the 

 head and thorax. 



The gonapophyses belong to the genital apparatus, 

 and will be described later. 



III. DISSECTION OF THE COCKEOACH. 



Fix the animal down with the dorsal surface upwards. 

 This may be done by drying it with blotting paper, and 

 immersing its under surface in melted paraffin or wax, and 

 holding it in this position till the wax is cool ; or it may be 

 fixed to a board by means of small pins passed through the 

 lateral regions of the mesothorax and of the abdomen. 



Cut off the elytra and the wings. Carefully cut through 

 the terga of the abdomen and thorax close to each side, and 

 remove the terga, avoiding injury to the heart, which lies just 

 beneath. 



A. The Circulatory System. 



1. The heart is a straight chambered tube running along 

 the mid-dorsal line of the abdomen and thorax. It 

 receives blood through lateral paired openings, 

 arranged segmentally, and drives it forwards by 

 rhythmical contractions. 



B. The Digestive and Excretory Systems. 



The alimentary canal, with its glandular appendages, is 

 situated almost entirely in the abdomen, and is enveloped in 

 an opaque-white, dendritic mass, the fat-body. 



Expose and unravel the alimentary canal and its append- 

 ages. In dissecting the salivary ducts great care must be 

 taken not to injure the nervous system in the head. 

 1. The alimentary canal is short, and slightly convoluted 

 in its hinder part. It may be divided according to 

 its mode of development into three regions : viz. 

 the stomatodo3um and the proctodoaum, which are 

 invaginations of the anterior and posterior ends 



