CH. xxvi.] KM I) BLOOD-CORPUSCLES. 4 1 7 



A property of the red corpuscles, which is exaggerated in 

 inflammatory blood, is a tendency to adhere together in rolls 

 or columns (rouleaux), like piles of coins. These rolls quickly 

 fasten together by their ends, and cluster ; so that, when the 

 blood is spread out thinly on a glass, they form an irregular 

 network (fig. 342). 



Action of Reagents. Considerable light has been thrown on the 

 physical and chemical constitution of red blood-cells by studying the effects 

 produced by mechanical means and by various reagents ; the following is a 

 brief summary of these reactions : 



Water. When water is added gradually to frog's blood, the oval 

 disc-shaped corpuscles become spherical, and gradually discharge their 

 haemoglobin, a pale, transparent stroma being left behind : human red blood- 

 cells swell, change from a discoidal to a spheroidal form, and discharge 

 their pigment, becoming quite transparent and all but 

 invisible. j^ _*i, 



Physiological saline solution causes no effect on the red ;gj^ 



corpuscles beyond preventing them running into rouleaux. A 



If a stronger sale solution is used, the corpuscles shrink and 

 become crenated (fig. 345). 



Dilute acetic acid causes the nucleus of the red blood-cells hition 

 in the frog to become more clearly defined ; if the action is tion). 

 prolonged, the nucleus becomes strongly granulated, and all 

 the colouring matter seems to be concentrated in it, the surrounding cell- 

 substance and outline of the cell becoming almost invisible ; after a time 

 the cells lose their colour altogether. The cells in the figure 

 (fig. 346) represent the successive stages of the change. A 

 similar loss of colour occurs in the red corpuscles of human 

 blood, which, however, from the absence of nuclei, seem to 

 disappear entirely. 



Dilute alkalis cause the red blood-cells to dissolve slowly, 

 and finally to disappear. 



Chloroform added to the red blood-cells of the frog causes Fig. 346. Effect 

 them to part with their haemoglobin ; the stroma of the cells of w*> c acid- 

 becomes gradually broken up. A similar effect is produced 

 on the human red blood-corpuscles. 



Tunnic acid. When a 2 per cent, fresh solution of tannic acid is applied 

 to frog's blood it causes the appearance of a sharply- 

 defined little knob, projecting from the free surface 

 (Roberts' macula') : the colouring matter becomes at 

 the same time concentrated in the nucleus, which grows 

 more distinct (fig. 347). A somewhat similar effect is 

 produced on the human red blood-corpuscle, the colour- 

 ing matter being discharged and coagulated as a little K _ .. 

 knob of hasmatin on the surface of the stroma. tannin. 



Boric acid. A 2 per cent, solution applied to 



nucleated red blood-cells (frog) will cause the concentration of all the 

 colouring matter in the nucleus ; the coloured body thus 

 formed gradually quits its central position, and comes to be 

 partly, sometimes entirely, protruded from the surface of 

 the now colourless cell (fig. 348). The result of this experi- _. 

 ment led Briicke to distinguish the coloured contents of the 

 cell (zoo id) from its colourless stroma (aeuid). When applied 

 to the non-nucleated mammalian corpuscle its effect merely resembles that 

 of other dilute acids. 



K.P. B K 



