INFLUENCE OF THE VESSELS UPON NUTRITION. 155 



degree than others to attract certain substances from the 

 neighbouring blood. 



If we consider the possibility of such attraction with a 

 little more attention, it is peculiarly interesting to ob- 

 serve the behaviour of parts, which are at a certain dis- 

 tance from the vessel. If we apply a definite stimulus, 

 for example, a chemical substance, a small quantity of 

 an alkali I will suppose, directly to any part, we see that 

 this shortly afterwards takes up more nutritive matter, 

 so that even in a few hours its size becomes considerably 

 increased, and that, whilst before we were perhaps 

 scarcely able to distinguish anything in its interior, we 

 now find an abundant, relatively opaque material within 

 it, in no wise composed of alkali which had made its way 

 in, but essentially containing substances of an albuminous 

 nature. Observation shows that the process in all vas- 

 cular parts begins with hypersemia, so that the idea rea- 

 dily presents itself that the hypersemia is the essential and 

 determining cause. But if we investigate the matter 

 more minutely, we find it difficult to understand how the 

 blood, which is in the hypersemic vessels, can contrive 

 only to act just upon the irritated part, whilst other 

 parts lying in the immediate vicinity are not affected in 

 the same manner. In all cases in which the vessels are 

 the immediate originators of disturbances which take 

 place in a tissue, these are most marked in the immediate 

 neighbourhood of the vessels and in the district which they 

 supply (vascular (or vessel-) territory). If we introduce 

 an irritating, as. for example, a decomposing body into 

 a blood-vessel, a fact that has been established by me 

 upon a large scale when tracing out the history of em- 

 bolia, we by no means see that the parts at a distance 

 from the vessel are the principal seats of active change, 

 but that this is in the first instance manifested in the wall 

 of the vessel itself and then in 'the adjoining histological 



