Nova Acta Academice JS^ahiroi Curiosorum. 475 



" *2. The dorsal vessel pulsates most strongly at its abdominal 

 extremity; and although as a whole it corresponds to the idea of a heart, 

 yet its lower portion (frequently much expanded) is that which more 

 especially coincides with this idea. 



" *3. In the course of the dorsal vessel there are no special enlarge- 

 ments, nor any lateral ramifications of blood-vessels demonstrated either 

 by anatomy or by the microscope, t 



" *4. The dorsal vessel is therefore truly a heart, that is to say, a 

 central organ accelerating and regelating the circulation, and receiving 

 and expelling the blood by means of primary vessels, but not itself 

 ramifying immediately and from its sides into smaller vessels. 



" *5. The dorsal vessel receives the systemic blood at its abdomi- 

 nal extremity through venous apertures, and expels it at its termination 

 near the head. This is proved partly by microscopic observations, in 

 which the injection and expulsion (the latter, for example, in the head 

 of Lampyris) may be immediately seen, and partly by anatomical ob- 

 servations of the subdivision of the dorsal vessel at both extremities, as 

 noticed by Mayer, Miiller, and Schultz. 



" 6. The circulation of the blood in other parts of the body takes 

 place partly without vessels in free streams, and partly in vessels. I re- 

 regard this law, for the present, as hypothetical, because although it is 

 certain that the blood, in the wings for example, circulates through 

 vessels, it is not positively ascertained that in those parts of the body 

 in which the microscope detects streams of blood, but recognizes no 

 vascular parietes, the latter are actually wanting. 



" *7. As the current of the blood within the dorsal vessel is directed 

 forwards towards the head, so without that vessel it is directed back- 

 wards towards the abdommal extremity. 



" 8. This circulation is probably only the further developement 

 of a simple constant circular current, at first destitute of parietes, which 



f In a note on this passage, Dr. Cams refers to the lateral apertures in the 

 dorsal vessel, for the imbibition of the blood, (described by M. Straus-Durck- 

 heim, but not detected by Herold, Marcel deSerres, Meckel, Miiller, or himself), 

 which he seems unwilling to admit witiiout further proof. 



