92 



Annelides, 



lerably well seen without the aid of injection, on account of the dark 

 red colour of the circulating fluid ; and some of the smaller branches 

 may be readily discerned by placing a leech, which has been kept for 

 some time without food, in rectified spirit (alcohol), which coagu- 

 lates the blood in the vessels, and at the same time presei*ves its red 

 colour, as was, I believe, recommended and first practised by Dr. 

 Kurzman. 



a a. Lateral blood-vessels of the horse-leech. b. Dorsal vessel, c. Abdominal vessel. d. Portion 

 of latersd vessel highly magnified. e. Muscular fibre of tunic. /. Muscular fibre of oesophagus. 



g. Blood-disks. 



For our present purpose it will be merely necessary to consider the 

 vascular system as composed of four longitudinal trunks, with their 

 communicating branches. Of these four trunks two occupy the sides 

 of the body, and from this circumstance they are termed the lateral 

 vessels (fig. a a), whilst the remaining two are placed, one on the dorsal 

 (fig. b), the other on the ventral surface (fig. c), in the median line of the 

 body. These two last trunks communicate with each other by smaller 

 branches, termed dorso-ahdominal, which correspond with each seg- 

 ment of the body, and also with the lateral vessels, by a series of 1 

 branches termed dorso4ateral. The two lateral vessels are considered 

 to form the arterial portion of the system, while the dorsal and ventral 

 vessels correspond to the venous. This distribution of the vessels 

 may be readily understood by reference to the figure, where the arte- 

 rial system is represented by the light vessels, the venous by the dark 



