6 Mr. C. Robertson on the Organs of 



Injections show that the whole of the venous blood is returned 

 to the sinus by the three veins 1 have described before it is dis- 

 tributed to the pulmonary capillaries ; none of it returns along 

 the anterior border of the mantle and so into the capillaries. 

 If a transverse section is made of the intestine, venous sinus, and 

 duct of the kidney, about the middle of their course (fig. 2 c), they 

 will be found arranged in the following manner. The intestine 

 has the venous sinus on its outer border, and the duct of the 

 kidney on its inner ; the duct of the kidney is much stouter 

 than the sinus, but both have about the same calibre. 



There is not much difficulty in making a successful injection 

 of the venous system from the sinus, by the side- of the rectum, 

 the injection spreading very readily from the veins into the 

 capillaries, and, if not too much pressure is used, without 

 extravasating amongst the viscera*. 



As I have before observed, the capillaries may be injected from 

 the aorta, or by thrusting a pipe into the tentacle, or from the 

 venous sinus. Injection performed in either of these ways fills 

 a rich plexus of vessels on the whole of the digestive tract, the 

 generative organs, mantle, and foot, before presenting any trace 

 of lacunae amongst any of these organs. I have repeatedly in- 

 jected from the aorta, and have found the capillaries richly in- 

 jected, as well as the venous system, without any trace of lacunae 

 or intervisceral spaces being observed between the arteries and 

 veins. I have therefore come to the conclusion that the vascular 

 system is closed in Helix pomatia, and that the arteries and 

 veins are connected by a capillary system, and the blood is not 

 shed into lacunae in any part of the body. If the injection of 

 these delicate animals is not very carefully performed, and the 

 body quite soft and flexible before the injection is thrown in, it 

 will very readily form large masses amongst the viscera. If one 

 of these masses from a warm injection is carefully picked out, 

 and placed in warm water, the whole of the injection readily 

 dissolves, and does not leave any trace of enveloping membrane, 

 which, I think, shows conclusively that if lacunae do exist in the 

 body, they are not dilatations of the venous system, but must be 

 spaces excavated in the body without any independent walls. I 

 have repeatedly examined the whole of the abdominal cavity, for 

 the purpose of making out any communication between it and 

 the venous system, without finding any. If the veins have any 

 direct communication with the cavity of the body, and a size 



* The vessels of Helix algira are figured by Carus and Ottone, part 6. 

 tab. 2. fig. 5, from Erdl's ' Dissert, inauguralis de Helicis algiroe vasis 

 sanguiferis, 1840/ which I have not seen. Siebold considers that they are 

 arteries which are figured (Anatomy of the Invertebrata, p. 248); but I am 

 quite confident that they are veins which are figured, and that Erdl is right. 



