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TEXT-BOOK OF ENTOMOLOGY 



means of muscular fibres, are united with the chamber and with their valves. 

 These pyriform bodies appear as vesicles or cells with granular contents, besides 

 some nuclei with nucleoli. They are of very small size. According to the 

 measurements of Dogiel, in the larva of Corethra plumicornis, they are 0.02 to 

 0.1 mm. long, and 0.00 to 0.08 mm. broad. He regards these peculiar bodies as 

 apolar nerve-cells of the heart. (Kolbe.) 



Besides the venous openings of the heart which open into the pericardial 

 region, Kowalevsky has discovered, in the heart of some Orthoptera (Caloptenus, 

 Locusta, etc.), five pairs of openings by which the cardiac chambers receive the 

 blood of the peri-intestinal region. Graber had divided the ccelom of insects 

 into three regions (pericardial, peri-intestinal, and perineural regions), and 

 hitherto only a union of the heart with the pericardial region by slit-like open- 

 ings was known. These openings are symmetrically distributed on five abdomi- 

 nal segments ; each section of the heart in this region has, therefore, four 



A 



C 



FIG. 373. A, part of the heart of Dyticus inarginafis, showing- the spiral arrangement of the 

 muscular fibres ; c, closed, t>, open, valve ; a, dorsal diaphragm with interwoven muscular fibres ; 

 b, arrangement of fibres, recalling the screw-like features of the fibres of the human heart ; </, narrow 

 end. -B, diagrammatic figure of the valvular openings, with the terminal flap (e), and the cellular 

 valve, of a May beetle ; <t, valvular opening of a dipterous larva, with the interventricular valve (/>). 

 C, abdomen of a mole-cricket, ventral view; c, the segmented heart; a, aorta; b, segmented dia- 

 phragm under it. After Graber. 



openings, which are all of a truly venous nature. These openings, called 

 cardio-ccelomic apertures, are visible to the naked eye, being situated on conical 

 papillae of the walls of the heart. These papilhe pass through the outer dia- 

 phragm, and open into the peri-intestinal part of the ccelom, in the Acrydiidre 

 directly, in the Locustidae through special canals. The cells of the papilla? are 

 spongy, possessing large nuclei, and similar, as a whole, to glandular cells. 

 (Comptes rendus, cxix, 1894.) 



The mechanism by which the ostia are closed consists, according to Graber, 

 of an co-shaped muscle passing around the two openings, and which, being inter- 

 laced, is sufficient to close the openings. But this is not all. The fore and 

 hinder edge of the ostia project, leaf-like, into the cavity of the heart, and thus 

 form, with the outer walls, two valves which, during the systole, filled with the 

 blood rushing in, not only hermetically close the lateral openings, but also, by 

 the simultaneous closure of the entire chamber by the circular muscles in the 

 middle of the same, the two valves, simultaneously approaching each other, so 



