48 ORGANISED FLUIDS. 



incorporation with each other. This view is far less tenable 

 than that of Mr. Addison, and neither is supported by a 

 sufficient number of facts to render its accuracy any thing 

 but exceedingly problematical. 



That the white corpuscles of the blood are engaged in the 

 process of nutrition is proved by the fact, that they are found 

 in increased quantities in vessels which are actively adminis- 

 tering to that function. This accumulation is witnessed also 

 in the capillary vessels of any parts which are subjected to 

 irritation of any sort, and in which, as a consequence of that 

 irritation, there is augmented action. 



The gradual collection of the white corpuscles of the blood 

 in the capillary vascular network, may be seen to the 

 greatest possible advantage in the tongue of the frog, as also 

 in the web of the foot of that conveniently formed creature, 

 as the result of continued exposure of the parts to the action 

 of air.* 



But it is not alone the aggregation of the colourless 

 corpuscles that may be seen in the minute vessels ; their 

 escape from those vessels may likewise be determined by a 

 prolonged examination of them. If, after the continuance 

 of this congested condition of the vessels for twenty-four or 

 thirty-six hours, they are again examined, it will be obvious 

 that certain of the corpuscles have become entangled in the 

 fibres which form the walls of the vessels, and that certain 

 others have altogether passed the boundaries of the vessels, 

 and now lie external to them. 



Again, it is asserted, that the epithelial cells are derived 

 from the white corpuscles of the blood. If this be correct, it 

 would appear that the escape of these corpuscles is a perfectly 

 normal and natural occurrence. 



* Mr. Addison states that, in order to insure a satisfactory exhibi- 

 tion of this important and curious phenomenon, the parts should be 

 irritated in some manner, as by immersion for a minute or two in warm 

 water at a temperature of 95 Fahrenheit, or by permitting a few 

 crystals of common salt to dissolve upon it. These methods I have tried, 

 and have found that they have usually resulted in the entire cessation of 

 the circulation in the capillaries, and this has been also the case even 

 when a weak solution of salt in water has been applied. 



