CHAP. II.] THE BLOOD. 125 



The colourless corpuscles are obviously much lighter than the 

 coloured, as is evidenced (1) by their always being found in greater 

 abundance near the upper surface of a blood clot; (2) by their 

 forming a separate white layer on the surface of the red corpuscles, 

 when horse's blood is cooled with the object of separating the corpuscles 

 from the liquor sanguinis. 



The colourless corpuscles exhibit obvious adhesiveness even when 

 contained in the blood-vessels of the living body, an adhesiveness which 

 causes them to cling one to the other when they meet, and to foreign 

 bodies or blood clots which may happen to project into the blood stream. 



The great mass of the protoplasm of the colourless corpuscle is 



undoubtedly proteid in its nature, the proteid matter having associated 

 with it smaller quantities of other principles, and imprisoning the 

 nucleus or nuclei which we may provisionally assume to be composed 

 of that somewhat non-descript, phosphorus-containing, non-digestible, 

 mucin-like body, Nuclein (see p. 82). 



The protoplasm of the colourless corpuscles appears to undergo, at 

 least partial, coagulation at 40 0. It swells and becomes transparent 

 when treated with acetic acid, which renders the nuclei much more 

 sharply defined and distinct. 



The protoplasm swells and ultimately dissolves in 10 p.c. solution 

 of NaCl, leaving the nuclei undissolved. The salt solution thus 

 obtained is precipitated by the addition of a large quantity of water, 

 is coagulated by heat and by mineral acids. 



The colourless corpuscles sometimes contain within them minute 

 fat-granules. 



Many of the white corpuscles of the blood present, when treated 

 with a solution of iodine in iodide of potassium and water, a reddish 

 mahogany colour, which is due to their containing Glycogen. The 

 solution recommended to be used is one made by dissolving 

 1 gramme of iodine and 2 grms. of potassium iodide in 100 c.c. 

 of water. "The main substance of the corpuscles is uniformly 

 stained of a deep yellow, but many contain groups of mahogany- 

 stained granules, and from others are seen to exude after a time 

 pellucid drops of varying size, which become tinted of a mahogany or 

 port wine colour, and no doubt contain glycogen 1 ." 



The average proportion of colourless to coloured corpuscles is 

 liable to considerable variations consistently with health. It under- 

 goes physiological fluctuations which are related to the process 

 of digestion, viz. the colourless corpuscles increase after the in- 

 gestion of food, and diminish during fasting, a fact explained 

 in great measure by the fact that in the former case a larger 

 influx of colourless cells takes place through the thoracic duct. 

 The origin and destination of the colourless corpuscles, though 

 perhaps beyond the scope of this work, will be shortly treated of 

 under l lymphatic glands.' 



1 Schafer, A Course of Practical Histology. Smith, Elder and Co., 1877. 



