156 LECTURE VI. 



elements. But if we apply the stimulus directly to the 

 tissue, the central point of the disturbance will always 

 continue to be that at which the stimulus produced ita 

 effect, just the same whether there are vessels in the 

 neighbourhood or not. 



We shall hereafter have occasion to return to this sub- 

 ject, and my only object here was to lay this fact before 

 you in its general features, and thus repel the ordinary 

 conclusion, which is as convenient as it is fallacious, that 

 hypersemia (in itself passive) exercises a directly regulat- 

 ing influence upon the nutrition of tissues. 



If a special proof were still required in order to com- 

 plete the refutation of this assumption, which in an ana- 

 tomical point of view is utterly untenable, we find a 

 most apposite argument in the experiment above men- 

 tioned of the section of the sympathetic. In an animal 

 the sympathetic may be divided in the neck ; thereupon 

 a state of hyperaemia ensues in the whole of that half of 

 the head, the ears become dark red, the vessels greatly 

 dilated, the conjunctiva and nasal mucous membrane 

 turgidly injected. This may continue for days, weeks, 

 or months, without the least appreciable nutritive dis- 

 turbance necessarily arising therefrom ; the parts, 

 although gorged with blood, are yet, as far at least as 

 we are at present able to judge of this, in the same state 

 of nutrition as before. If we apply stimuli sufficient to 

 produce inflammation to these parts, the only thing that 

 we remark is, that the inflammation runs its course more 

 quickly, without exhibiting either in itself or in the na- 

 ture of its products anything essentially unusual. 



The greater or less quantity of blood, therefore, which 

 flows through a part is not to be regarded as the only 

 cause of the changes in its nutrition. There is, I sup- 

 pose, no doubt that, when a part, which is in a state of 

 irritation, receives more blood than usual, it is also able 



