444 ON HIRITANTS AND COUNTER-IRRITANTS. 



this arrangement to secure a full supply of blood whenever it is 

 wanted is obvious. Now, as I have already said, a copious blood- 

 supply not only enables tlie tissues to grow rapidly, but to repair 

 themselves rapidly when injured, and a scanty blood-supply^ 

 on the contrary, will cause repair to be slow, and will even 

 induce death and destruction of a part without any other lesion ; 

 as, for example, when the circulation is stopped by an embr)lus. 

 The effects of copious blood-supply in accelerating repair have 

 been beautifully shown by the experiments of Sinitzin.* When 

 the hfth nerve is divided witliin the skull, ulcers form on the 

 cornea, eyelids, and lips. If the superior-cervical ganglion i.s- 

 torn out, so that the vaso-motor nerves of the vessels of the 

 face are destroyed, and the supply of blood to it increased alter 

 these ulcers have formed, they heal up speedily ; and if the- 

 ganglion is torn out before the fifth nerve is cut, they do not 

 form at all. That the beneficial effect of evulsion of the 

 ganglion is due to the free supply of blood which it produces,, 

 is shown by the fact that it has no action whatever if the carotid 

 of the same side is ligatured, so as to prevent the destruction of 

 the vaso-raotor nerves from increasing the current. As we have- 

 already seen, a still greater supply of blood is secured to a part 

 by irritating its sensory nerves than by dividing its vaso-motor 

 ones, and the utility of this in repairing injured parts is now 

 obvious. When a grain of sand falls into the eye, it irritates 

 the sensory nerves, and immediately the vessels of the conjunc- 

 tiva fill, as Sinitzin noticed them to do, after evulsion of the- 

 sympathetic ganglion, and the free supply of blood is ready to 

 assist the repair of any damage caused by the sand to the- 

 delicate structures of the eye, besides supplying materials tO' 

 the lachrymal gland for the purpose of washing away the- 

 offending body. If the grain of sand is now removed, the 

 vessels contract, and the tears being wiped off everything looks 

 as before. There has been congestion, but no inflammation. 

 But if the sand remains longer, inflammation occurs, sero- 

 fibrinous exudation takes place under the conjunctiva, or pus 

 mav even be formed. 



If we examine the process of inflammation more narrowly by 



* Centralbtatt d. med. TFissenschaften, 1871, p. 161. 



