CHANGES IN VASCULAR PATTERNS 



1263 



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fig. 9. Effect of denervation 

 upon collateral circulation. In 

 the upper half of the drawing is 

 shown the collateral circulation 

 22 days after interruption of the 

 left femoral artery in a rabbit. 

 In the lower half the more exten- 

 sive collateral circulation in a 

 comparable preparation but with 

 the crural and sciatic nerves cut 

 at the time of the arterial ligature. 

 At the right above is shown a 

 section of the profunda femoris 

 on the control side, and, below, 

 a comparable section after func- 

 tion for 8 weeks as a collateral 

 vessel following ligature of the 

 femoral artery. There is hyper- 

 plasia as well as hypertrophy of 

 the muscle. [From Nothnagel 

 (i29>] 



had become intrigued by Leriche's studies of the 

 periarterial sympathetic nerves. Mulvihill & Harvey 

 (125) found that with sympathectomy the temperature 

 of an extremity did not fall after ligature of the 

 external iliac artery (fig. 10). Theis (173) and later 

 Longland (108) confirmed this observation by various 

 methods. Both indicated the persistence of the effect 

 over several months. Injection with alcohol of the 

 main artery beyond a ligature in the anterior ex- 

 tremity of the dog, a procedure that was presumed 

 to produce a destruction of the sympathetic nerves 

 within it, seemed to result in a better development 

 of collateral circulation than in the leg of the control 

 side (91, 92). 



Turning to the "microcirculation," Fulton et al. 

 (57) provide a description of several orders of nerve 

 plexuses related to the small vessels in the cheek 

 pouch of the hamster. The networks are sufficiently 

 rich to innervate all the smooth muscle cells of the 

 vessels. The development of a complement of non- 

 medullated nerve fibers in newly formed arterioles 

 in chamber preparation of the rabbit's ear has been 

 demonstrated by the Clarks (37). They have estab- 

 lished that only vessels supplied with such fibers are 

 capable of spontaneous contraction. The bearing of 

 these observations on the development of collateral 

 circulation remains for further exploration. 



In 1958, North & Sanders (127) reported that the 

 innervation of the mouse ear seemed to have no 

 effect on the growth of collateral vessels. 



The existence of a "basal vascular tone"' of local 

 muscular rather than neural origin has been con- 

 sidered by Folkow (53, 54). Evidence for an appar- 

 ently nonneural dilator response, probably trans- 

 mitted by the musculature of the vessel itself, has been 

 adduced by Hilton (75). He found that cocainization 

 of a femoral artery feeding actively contracting 

 muscle abolished its dilatation, while cutting the 

 nerve to the extremity and curarizing the animal 

 did not. This dilator response traveled up the artery 

 at a slow rate, of the order of 10 cm per sec. Such 

 phenomena may have a bearing on the total problem 

 of the reaction of collaterals. 



When the influence of the nervous system, and 

 possibly also of intrinsic myogenic influences, is con- 

 sidered, it is clear that the important effect relative 

 to collateral circulation is the lysis of vascular tone. 

 This is expressed essentially in the alteration of 

 mechanical forces. Possible influences on the growth 

 of vessels are as yet unknown. 



chemical factors. There are at least four ways in 

 which chemical substance could affect collateral 

 circulation: /) By regulating vasodilatation. 2) By 

 controlling the proliferation of new vessels. 5) By- 

 stimulating and inhibiting the growth of vessels. 

 (Growth itself is obviously a chemical process, 

 although it could be initiated by mechanical or 

 chemical factors.) ./) By guiding vessels to specific 

 destinations. 



