THE L\n-R\.lL STRUCTURE OF ANTS. 



47 



into the head, bathes all the organs and then leaves it through the neck 

 to traverse the whole thoracic cavity in an antero-posterior direction. 

 After having passed through the much constricted peduncle of the 

 petiole and postpetiole, it enters the gaster and flows through two 

 passages, separated by a diaphragm that divides the body cavity into a 

 ventral, or neural, and a dorsal, or visceral, sinus. One current descends 

 through the dorsal, another through the ventral sinus, following the 

 latter to the tip of the gaster. The dorsal sinus, which is very large 

 and supplies the heart with the blood it propels into the head, is thus 



I 



FIG. 24. Transverse section through heart of Myrmica rubra. (Janet.) A, Through 

 region of rectum ; c, heart ; sf, suspensory filaments ; am, aliform muscle ; pc, peri- 

 cardia! cells : /, fat-cells ; n, urate-cell ; oe , cenocyte ; ch, dorsal integument ; r, dorsal 

 wall of rectum. B, Diagram to illustrate position of heart, suspensory filaments and 

 aliform muscle during systole (continuous lines) and diastole (dotted lines). 



supplied simultaneously by the posterior portion of the postpetiole and 

 the posterior portion of the ventral sinus of the gaster." 



Connected with the circulatory system are some four different kinds 

 of cells, which are suspended either singly or in clusters in the blood 

 current. These are the pericardial cells (Fig. 24, pc}, the oenocytes 

 (0<?),the adipocytes (/), forming the fat body, or corpus adiposum and 

 the urate cells ('). The pericardial cells are of small size and arc 



