PHENOMENA. ' 7-- 



pouches are not, however, peculiar to the inflammatory state, 

 and they have been ascribed to structural derangement of the 

 walls of the vessels, in consequence of which they cannot present 

 an equable resistance to the column of blood, and consequently 

 the blood becomes extravasated into the surrounding textures. 



Some have affirmed that constriction of the vessels never 

 takes place prior to their ddatation. This, as already ex- 

 plained, has arisen from the kind and strength of the irritant 

 used by these observers ; whilst others state that, during con- 

 traction, the blood is seen to flow more rapidly through them, 

 and that this is explained by the well-known fact that 



Fig. 1. — An exact copy of a portion of the web in the foot of a young frog, after 

 a drop of strong alcohol had been placed upon it. The view exhibits a deep-seated 

 artery and vein, somewhat out of focus ; the intermediate or capillary plexus run- 

 ning over them, and pigment cells of various sizes scattered over the whole. On 

 the left of the figure the circulation is still active and natural. About the middle 

 it is more slow, the column of blood is oscillating, and the corpuscles crowded 

 together. On the right, congestion, followed by exudation, has taken place. 



a. A deep-seated vein, partially out of focu^. The current of blood is of a deeper 

 colour, and not so rapid as that in the artery. It is running in the opposite direc- 

 tion. The lymph space on each side, filled with slightly yellowish blood plasma, is 

 very apparent, containing a number of coloiurless corpuscles^ clinging to, or slowly 

 moving along, the sides of the vessel. 



b. A deep-seated artery, out of focus, the rapid current of blood allowing nothing 

 to be perceived but a reddish-yellow broad streak, with lighted spaces at the sides. 



Opposite c, a laceration of a capillary Vessel has produced extravasation of blood, 

 which resembles a brown spot. 



At d, congestion has occurred, and the blood corpuscles are apparently merged 

 in one semi-transparent reddish mass, entirely filling the vessels. The spaces of the 

 web between the capillaries are rendered thicker and le>s transparent, partly by 

 the action of the alcohol, partly by the exudation. This latter entirely fills up the 

 spaces, or only coats the vessels. 200 diameters. — (Bennett.) 



liquids flow more rapidly through a narrowed tube. This is not 



