410 FUNCTIONS OF THE NERVES. [ch. in. 



there are nervous loops and nooses at the termination of the 

 arteries and roots of veins, similar to those which are seen to sur- 

 round the larger arteries in many places ; and they opined that 

 these loops could be tightened or relaxed, and so be able to 

 admit blood to the part or retain it. Haller, together with some 

 of his disciples, followed Willis in adopting this opinion ; but 

 when he learnt, from experiments, that the nerves do not con- 

 tract when stimulated, he rejected the doctrine. Some located 

 muscular sphincters at the terminations of the arteries and 

 roots of the veins, which constricting the vessels, and causing 

 the blood to accumulate above the constriction, so inundated 

 the lateral vessels : Boerhaave in particular propounded this 

 opinion in his theory of obstruction,^ and also founded his 

 theory of inflammation upon it. But many and weighty ob- 

 jections have been raised against this production of accu- 

 mulation and inflammation by obstruction and constriction 

 only; for obstruction of a vessel does not cause such an 

 accumulation of fluid, anterior to the obstruction, because it 

 easily finds an exit through the lateral vessels so obvious in every 

 part of the body ; and the comparison of a river swelling from an 

 obstruction, and inundating the adjoining parts, does not apply 

 to our vessels ; for if one, or even many of them, be obstructed, 

 there still remain innumerable lateral vessels, through which 

 the fluids find a free outlet. For this reason, Haller found that 

 the trunk of an artery, when tied, became swollen indeed for a 

 moment, between the ligature and the heart, and manifested 

 T)ne or two pulsations ; but so far is it from the fact, that 

 the impetus of the fluids is directed against the ligature, that 

 rather the canal is contracted, and it impels the blood into 

 the communicating arteries, until that which was tied is quite 

 empty. The same thing is shown by the umbilical arteries, 

 which also become empty, and impervious. WinterP fully 

 sets forth these and other arguments of distinguished men, 

 and proves that the fluids do not rush towards an obstruction, 

 but rather prefer to pass away by the lateral and unobstructed 

 vessels ; consequently, no congestion and no inflammation can 

 arise from an obstruction only, but the stimulus of the nerves 

 is the cause, which immediately excites the fluids to accumulate 

 more copiously in the vessels subjected to them. Moreover, 

 ' Aphoris., 113. ^ Nova Theoria Inflammationis, p. 19. 



