Nova Acta Academie Nature 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 regulating 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 abdominal extremity. 
«* §. This circulation is probably only the further developement 
of a simple constant circular current, at first destitute of parietes, which 
+ In a note on this passage, Dr. Carus refers to the Jateral apertures in the 
dorsal vessel, for the imbibition of the blood, (described by M, Straus-Durck- 
heim, but not detected by Herold, Marcel de Serres, Meckel, Miiller, or himself), 
which he seems unwilling to admit without further proof, 
