RED CORPUSCLES OF THE BLOOD. 



209 



only when the light traverses a number of corpuscles that a distinct red colour is 

 produced. 



In consequence of the biconcave shape of the corpuscle, it looks darker in the 

 middle than at the edge when viewed with only a moderate magnifying power, or at 



Fig. 240. HUMAN RED CORPUS- 



CLES (A) AND BLOOD CORPUSCLES 

 OF THE FROQ (B) PLACED SIDE 

 BY SIDE TO SHOW RELATIVE 

 SIZE. 500 DIAMETERS. 



1, shows their broad surface ; 

 2, one seen edgeways ; 3, shows 

 the effect of dilute acetic acid ; 

 the nucleus has become distinct 

 (from Wagner). 



a distant focus ; but the middle of the corpuscle appears lighter than the periphery 

 when a close focus or a very high magnifying power is employed. 



The red disks, when blood is drawn from the vessels, sink in the plasma ; they 

 have a singular tendency to run together, and to cohere by their broad surfaces, so 

 as to form by their aggregation cylindrical columns, like piles or rouleaus of money, 

 and the rolls or piles themselves join together into an 

 irregular network (figs. 239 and 241). Generally the cor- 

 puscles separate on a slight impulse, and they may then 

 unite again. The phenomenon will take place in blood 

 which has been in any way brought to a standstill within 

 the living vessels as well as in blood that has stood for 

 some hours after it has been drawn, and also when the 

 globules are immersed in serum in place of liquor san- 

 guinis. 



Fig. 241. RED CORPUSCLES 



COLLECTED INTO ROLLS 



(after Henle). 



It has been shown by Norris that disks which float completely 

 immersed in any fluid will, when the fluid comes to rest, tend 

 to adhere together in the form of rouleaus provided that the 

 surface of the disks is of a nature not to be wetted by the fluid 

 in which they float. Thus cork disks which have been weighted 



so that they neither rise nor sink in water do not adhere together so long as they are freely 

 wetted by the water, but if their surfaces are coated with a thin film of fatty substance the 

 disks tend to run together into rouleaus. As it is probable (see below, Structure of Red 

 Corpuscles) that the red disks do actually possess a superficial film of fatty substance, the facts 

 pointed out by Norris appear to suggest a reasonable explanation of the rouleau-formation 

 which occurs in blood which has been allowed to come to rest. 



The human blood-corpuscles, as well as those of the lower animals, often present 

 deviations from the natural shape, which are most probably due to causes acting 

 after the blood has been drawn from the vessels, but in some instances depend upon 

 abnormal conditions previously existing in the blood. Thus, it is not unusual for 

 many of them to appear shrunken and crenated, when exposed under the microscope 

 (fig. 239, c, c ; fig. 242, /), and the number of corpuscles so altered often appears to 

 increase during the time of observation. This is, perhaps, the most common change; 

 it occurs whenever the density of the plasma is increased by the addition of a neutral 

 salt, and is one of the first effects of the passage of an electric shock. The corpuscles 

 may become distorted in various other ways, and corrugated on the surface ; not 

 unfrequently one of their concave sides is bent out, and they acquire a cup-like figure. 



Gulliver made the curious discovery that the corpuscles of the Mexican deer and some allied 

 species present very singular forms, doubtless in consequence of exposure ; the figures they 

 assume are various, but most of them become lengthened and pointed at the ends, and then 

 often slightly bent, not unlike caraway-seeds. 



