116 



THE VASCULAR SYSTEM 



full action of the respiratory movements on the renal circulation 

 leads to diminished flow and oedema of the transplanted organ. 

 The capillaries and veins are naturally so arranged to run that 

 each muscular action of the body promotes the flow in them to- 

 wards the heart. It is important also that no bleeding take 

 place into the connective tissues during or after the operation, as 

 blood has an irritative effect and produces sclerosis. Bier has 

 utilised this property, and injected blood to excite callous forma- 

 tion in cases of pseudo-arthrosis. 



The experiments of Carrel bring just within the limits of the 



FIG. 6. Operation method of J. E. Sweet (Journ. Exp. Med. vii. 163, 1905) for 

 joining the portal vein and vena cava (Eck's operation). The double thread is the 

 wire of an electric cautery, and cuts the opening between the two vessels. 



possible the operation of transplanting from a man killed by an 

 accident such an organ as the thyroid into the neck or other part, 

 where it may carry on its function and compensate for thyroid 

 inadequacy in the recipient. Guthrie has succeeded in exchang- 

 ing the ovaries of black and white Leghorn hens, and finds the 

 foster-mother modifies the colour of the chicks hatched from the 

 eggs laid afterwards. The controls gave pure white or black 

 chicks. 



THE ELASTICITY AND CONTRACTILITY OF ARTERIES 



When the carotid artery of the ox or horse is exposed immedi- 

 ately after death, it is found to be soft and flaccid, more or less 

 flattened in section, with a large bore usually 5 or 6 mm. in diameter. 

 On exposure to the air, cooling, and especially on manipulation 



