670 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



roots ; and (b) those which are said to show that vaso-dilator fibres pass 

 out in the posterior roots. 



Most of those observers who support the presence of one class of 

 fibres, deny the existence of the other. 



Schiff was the chief advocate of the view that direct vasomotor 

 fibres are present in the anterior roots. His experiments were solely on 

 the effect of section of the nerves ; he did not stimulate them. Accord- 

 ing to him, 1 section of the anterior roots going to the sciatic in the dog 

 causes lasting and considerable rise of temperature in the foot and the 

 lower third (about) of the limb. Bernard, 2 on the other hand, cut the 

 lower lumbar and sacral nerves in the spinal canal, so that there was 

 complete paralysis and lack of sensation in the limb, and found no 

 increase of temperature of the foot. And this is in agreement with 

 general experience. 



Schiff 3 stated also that section of the anterior roots of the nerves running 

 to the brachial plexus causes rise of temperature in the lower part of the fore- 

 limb. This also is opposed to the results obtained by Bernard, by Cyon (1868), 

 and by other observers. 



Schiff's view was, that some vasomotor fibres run direct by the spinal 

 nerves, and that others run by way of the sympathetic. If this were the case, 

 stimulation of the anterior roots of the nerves supplying the limbs should 

 cause pallor in the foot. There is little difficulty in making the experiment in 

 a cat or dog Avith light- coloured feet, curari being given to paralyse the 

 muscles. I do not find that the nerves which supply motor and sensory 

 nerves to the foot have any effect upon the tint of the skin. The result is the 

 more obvious, in that complete pallor and subsequent flushing is produced by 

 stimulating the anterior roots of certain of the upper lumbar nerves (see p. 634), 

 which send no fibres to the foot except by way of the sympathetic. Even if 

 curari is not given, the difference in the action in the two sets of nerves is 

 unmistakable, although naturally some pallor may be caused by the contrac- 

 tion of the muscles of the limb. 



A considerable number of observers have arrived at the con- 

 clusion, that vaso-dilator fibres pass to the lower limb of the dog by way 

 of the posterior roots of the nerves which supply it with somatic fibres. 



The view was first advanced by Strieker. 4 He found that mechanical 

 irritation of the cut posterior roots of the sixth and seventh lumbar 

 nerves — he spoke of them as the fourth and fifth — caused constantly an 

 increase, and sometimes a very great increase, in the temperature of the 

 foot. He did not obtain constant results if curari or anaesthetics were 

 given, and in consequence found it necessary, as a preliminary to the 

 experiment, to cut the cord in the lower thoracic region, and wait for a 

 week to a fortnight, by which time the vascular dilatation produced by 

 the section had passed off. The experiment could then be made without 

 anaesthetics and without pain. Nor did he obtain satisfactory results 

 by electrical stimulation of the posterior roots, nor when adult dogs 

 were used. 



Cossy, 5 repeating Strieker's experiments, did not obtain constant 

 results, but sometimes found a rise of temperature from stimulating the 



1 Compt. rend. Acad. d. sc, Paris, 1862, tome lv. p. 400. 



2 Joum. de laphysiol. de Vhomme, Paris, 1862. 



3 Compt. rend. Acad. d. sc, Paris, 1862, tome lv. p. 425. 



4 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1876, Bd. lxxiv. Abth 3. : Med. Jahrb., 

 Wien, 1878, S. 409; cf. also Bonuzzi, ibid., 1885, S. 473. 



5 Arch, dephysiol. norm, etpath., Paris, 1876, p. 832. 



