154 ANATOMY. 



and has described it as a great pulsating * vein. Subsequently to him, 

 the other great entomotomists, Reaumur, Swammerdam, Bonnet, De 

 Geer, have recognised the same organ, and concur with him in repre- 

 senting it as a simple and wholly closed vessel. Even the very cautious 

 Lyonnet can consider it as nothing else ; but he described the lobes of 

 the dorsal vessel in greater detail, and has figured them more accurately 

 than any of his predecessors. In recent times Cuvier, in his " Com- 

 parative Anatomy," has repeated the descriptions of earlier anatomists, 

 and even after this organ had been subjected to the most painfully 

 patient investigations by Herold and Muller, its true structure has not 

 yet been ascertained. Carus f at last discovered the motion of a fluid 

 not only in the dorsal vessel but also in other parts of the body, and 

 shortly after him Straus Durckheim recognised a structure of the 

 dorsal vessel, which had been previously overlooked, which so entirely 

 agrees with the insect type of organisation, that no doubt can be enter- 

 tained of the correctness of his observation. My attention being drawn 

 to it by Straus' communications, I made investigations upon the 

 structure of the heart in several insects (for example, in the larva of 

 Calosoma sycophanta, Lamia cedilis, Termes fatalis, &c.), and I have 

 distinctly seen the valves and apertures mentioned by him. 



117- 



According, therefore, to these most recent observations, the dorsal 

 vessel (PI. XXII. f. 8 and 9.) is a thin canal composed of a delicate 

 membrane, it is largest in the abdomen, and gradually decreases to- 

 wards the head. In the abdomen it has on each side several apertures, 

 as well as lateral muscular lobes, whereby it is attached to the back; 

 where it enters the thorax it bends downwards (the same, f. 8. B.) that 

 it may pass through the narrow, more deeply situated opening into its 

 cavity, and then pursues its course above the oesophagus to the head, 

 where it terminates with a small orifice. The number of the lateral 

 apertures appears to vary (the same, a, a, a). Straus found eight in 

 Melolonllia, I could observe but four on each side in the larva of Calo- 

 soma. According to Midler's description of the heart there appears to 



* Compare his Dissert. Boinbyce. Lond. 1669, 4to. or his Collective Works, Lugd. 

 Bat. 1687, 4to., vol. ii. p. 20. 



t Entdeckung eines cinfachen, vom Herzen aus bleschlcunigten Krcislaufes in den 

 Larven netzfliiglichcr Insckten. Leipz. 1827. 4to. 



