130 VASCULAR SYSTEM. 



at the heart; they are wanting in the trunk of thecavaas- 

 cendens, in the emulgent veins, in the cerebral sinuses. 

 See Horner, Vol. II. p. 158. 



Q. How are the venous fibres best exhibited? 



*#. By plunging the veins into boiling water or concen- 

 trated acids, the horny hardening contraction takes place, 

 and the fibres are seen. 



Q. What distinguishes the venous parietes from the 

 arterial? 



.#. The penetration of cellular texture between the 

 fibres of the peculiar coat of the veins, into the common 

 lining membrane. This is not seen in the arteries. The 

 cellular coat of the veins is peculiarly filamentous. 



Q. To what extent do exhalation and absorption take 

 place in the veins? 



A. Only to subserve the purposes of nutrition. 



Q. Are the veins as abundantly supplied with nerves 

 as the arteries? 



#. They are not; a few ganglionic nerves supply them. 



Q. What induces you to believe that the nerves have 

 no effect on the contraction of the left side of the heart? 



/?. The fact that the right side is as abundantly sup- 

 plied with nerves as the left. We would therefore sup- 

 pose that nervous influence does not confer the difference 

 of ventricular power. 



Properties of the Vascular System with Black Blood. 

 1. Properties of Texture. 



Q. Are the veins extensible? 



JL. They are, but in a transverse direction; the arteries 

 are so longitudinally. 



Q. Have not recent investigations proved that the veins 

 are extensible longitudinally? 



