184 LECTURE VII. 



rived from post-mortem examinations, and the ignorance 

 of which has led to great errors. The colourless cor- 

 puscles possess namely, as was brought to light in the 

 discussion which Herr Ascherson, now here present, had 

 some time ago with E. H. Weber, the peculiar property 

 F 5g of being sticky, so that they 



readily adhere to one another, 

 and under certain circumstances 

 also cling fast to other parts, 

 when the red corpuscles do not 

 present this phenomenon. This 

 tendency to adhere to other 

 parts is particularly evident 

 when several of the corpuscles 

 are at the same time placed in a position which enables 

 them to stick together. Thus, in blood in which 

 there is an actual increase in the number of colourless 

 cells, it is extremely common for agglutinations to take 

 place among them, as soon as the pressure, under which 

 the blood flows, is diminished ; in every vessel, in which 

 the stream becomes slower, and the pressure weaker, 

 an agglutination of the corpuscles may take place. 



The adhesiveness (viscosity) of the colourless blood- 

 corpuscles produces besides this effect, that, as has been 

 shown by Herr Ascherson, when the blood is flowing as 

 usual through the capillary vessels, the colourless cor- 

 puscles generaUy float rather more slowly than the red, 

 and that, whilst these move along more in the centre of 

 the vessel in a continuous stream, a comparatively large 

 vacuity is left at the circumference, within which the 



Fig. 58. A. Fibrine clot from the pulmonary artery, and corresponding to its 

 terminal branches ; at a, a beset with largish patches, composed of heaps of white 

 cells ; at b, b, b with specks of an analogous nature. Natural size. 



B. A portion of one of these specks or heaps, composed of thickly crowded, 

 colourless blood-corpuscles. Magnified 280 diameters. 



