TISSUES OF THE BODY. 



109 



Fig. 111. Human blood-cells; a, after the action of water; 

 6, in evaporating blood ; c, dried up ; d, in coagulated 

 blood; e, arranged one over another in rouleaux. 



minuteness of the object. If the blood dry up rapidly in very thin layers, 

 the corpuscles have usually a round smooth outline, with a distinct pro- 

 jecting central portion (fig. Ill, c). 



If water be added to a drop of human blood, a completely different 

 picture is presented to the eye 

 of the observer. Far from be- 

 coming knobbed and jagged, the 

 cell preserves its circular smooth- 

 edged aspect, but the clear cen- 

 tral portion is no longer recognis- 

 able, and the yellowish border 

 stands out no more in relief 

 (fig. Ill, a). Close observation 

 teaches that the swelling up of 

 the cell commences at the border, 

 and that the encroachment of 

 the swollen portion it is which 

 causes eventually the two de- 

 pressions in the centre of the 

 blood -corpuscle to disappear. 

 As soon as a cell so treated 

 begins to roll, the important 

 difference caused by the loss of 

 its biconcave discoid figure becomes evident. We find the corpuscle 

 from every point of view spherical; it has swollen out into a globule 

 with diminution in diameter, down to 0'0061-0057 mm. Under the con- 

 tinued action of water this globule grows paler and paler (a to the right) 

 whilst the surrounding fluid acquires a yellowish tinge. Some cells are 

 very rapidly decolorised, others resist the action of the water for a longer 

 period. At last the corpuscle becomes so perfectly decolorised that it 

 can only be recognised by high magnifying power and in a shaded field ; 

 it is there seen as a very delicate, completely smooth-edged structure of 

 extreme paleness. During the whole procedure no nuclei make their 

 appearance. 



The employment of many watery solutions, such as those of sugar, gum 

 arabic, common salt, &c., produces an effect on the cells similar to that of 

 evaporation. But if these reagents be gradually diluted a degree of con- 

 centration is at length reached, at which no further change of form in the 

 cell can be observed. If the solutions be still further diluted, we observe 

 eventually the same effects produced as those of pure water, namely, a 

 puffing out and bleaching of the cell until it becomes invisible. It is 

 most interesting to mark on one and the same cell the changes produced 

 by the alternate addition of various fluids one after the other, changes 

 from the stellate wrinkled to the spherical tense form, and back again, 

 or rice versa. 



All observations which have been made up to the present teach the 

 absence of nuclei, and present to us the blood-corpuscle as a structure 

 whose substance rapidly absorbs and parts with water, in the first instance 

 swelling up and acquiring greater volume, and in the second shrinking to- 

 gether. We see, further, that the colouring matter of the cell-body is soluble 

 in water. Now, if we apply the results thus obtained to the corpuscle as it 

 circulates in the blood, we have in it an element which must, indeed, 

 engage in a lively interchange of matter with the fluid of the plasma, but 



