62 ON THE MOTION OF THE BLOOD. 



the united capacity of the branches is greater than that 

 of the trunk from which they arise. But I fear that 

 this is too general an assertion, and even that the mea- 

 sure of the diameter has been sometimes improperly 

 confounded with that of the area. I myself have never 

 been able to verify it, although my experiments have 

 been frequently repeated, and made, not on vessels in- 

 jected with wax, but on the undisturbed vessels of 

 recent subjects, on the innominata and its two branches 

 the right carotid and subclavian, on the brachial and 

 its two branches the radial and ulnar. * 



The inconstancy of the proportion between the capa- 

 city of the branches and trunks is clearly shewn by the 

 various size of the vessels under different circum- 

 stances, v. c. by the relative capacity of the inferior 

 thyroid artery in the infant and the adult ; of the epi- 

 gastric artery and also of the uterine vessels in a virgin 

 and a woman far advanced in pregnancy; of the 

 omental vessels during the repletion and vacuity of the 

 stomach, f 



91. The arteries, after innumerable divisions and 

 important anastomoses J connecting different branches, 

 terminate at length in the beginning of the veins. By 

 this means, the blood is conveyed back again to the 

 heart. The distinction between artery and vein at the 

 point of union, is lost. 



* See also J. Theod. Van Der Kemp, De Vita. Edinb. 1782. 8vo. p. 51. 



t This is remarkably observable in the adult stag, by comparing the areae of 

 the external carotid and its branches, during the spring, before the horns have 

 attained their full growth but are still covered with their downy integuments 

 (called in our language, der Bast), with such as they are after this covering 

 has fallen off. 



J Ant. Scarpa, SulF stnenrisma. Pav. 1804. fol. cap. 4. 



