252 THE VITAL FUNCTIONS. 



the real course which the blood takes while 

 circulating within them ; and we accordingly 

 find very great discordance in the reports of 

 different physiologists on this subject. De 

 Blainville asserts that in all the Annelida, the 

 blood in the dorsal vessel is carried backwards, 

 that is, from the head to the tail ; a motion, 

 which, of course, implies its return in the con- 

 trary direction either in the lateral or the abdo- 

 minal vessels. In the Nais, the Nereis, and 

 the Leech, these last vessels are two in number, 

 situated at the sides of the abdominal surface 

 of the body. Carus adds his testimony in favour 

 of this mode of considering the circulation in 

 the Annelida. On the other hand, Spix, Bon- 

 net, Sir Everard Home, and Dug^s describe the 

 course of the blood as quite the opposite of this, 

 and maintain that it moves backwards, or to- 

 wards the tail, in the abdominal vessels ; and 

 forwards, or towards the head, in the dorsal 

 vessel. Morren, who is the latest authority 

 on this subject, gives his testimony in favour 

 of the latter view of the subject, as far as relates 

 to the dorsal vessel of the Erpobdella vulgaris* 

 an animal, allied to the Leech, and already 

 noticed in the account of the mechanical func- 

 tions of this tribe :t but he considers the ab- 



* Hirudo vulgaris. (Linn.) Nephelis vulgaris. (Savigny). 

 t Vol. i, p. 271, where a delineation of this animal was given, 

 Pig. 130. 



