420 THE BLOOD [CH. XXVI. 



than the rest. They are termed microcytes, or hcematoblasts, and are 

 probably immature corpuscles. 



A property of the red corpuscles, which is exaggerated in inflam- 

 matory 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. 346). 



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 or envelope 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. This effect is due to osmosis. 

 Physiological saline solution causes no effect on 

 the red corpuscles beyond preventing them running 

 of saline scSu- into rouleaux. If a stronger salt solution is used, 



tion (crona- i,' I(; 350 Effect the corpuscles shrink and become crenated (fig. 

 tion). of acetic acid. 349) owing to osmosis of water outwards. 



Dilute acetic acid causes the nucleus of the red 



blood-cells in the frog to become more clearly defined ; if the action is 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. 350) 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, ether, and other reagents that dissolve fats 

 dissolve the fatty substance (lecithin, etc.) of the membrane 

 that surrounds the corpuscles, and so produce laking of the Fl( . 3 -j _Efj ect O f 

 blood. ' tannin. 



Tannic 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 dis- 

 tinct (fig. 351). A somewhat similar effect is produced on the human red blood- 

 corpuscle, the colouring matter being discharged and coagulated as a little knob 

 of haematin on the surface of the corpuscle. 



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 

 ~b formed gradually quits its central position, and 

 j comes to be partly, sometimes entirely, pro- 

 FIG. 352. Effect r , , ! Wffr _ truded from the surface of the now colourless 



of boric acid. ofheTt ' cell (fig. 352). The result of this experiment 



led Briicke to distinguish the coloured contents 



of the cell (zooid) from its colourless stroma or envelope (cecoid). When applied 

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

 dilute acids. 



Heat. The effect of heat up to 50 60 C. (120140 F.) is to cause the forma- 

 tion of a number of bud-like processes. 



