8 HISTOLOGY OF THE RED BLOOD-CORPUSCLES. 



blood of many persons crenates spontaneously a condition ascribed 

 to an active contraction of the stroma (Klebs), but it is doubtful if 

 this is the cause. Max Schultze observed that the red corpuscles 

 of the embryo-chick undergo active contraction. 



(B.) External Characters. Many agents affect the external char- 

 acters of the corpuscles. 



(a.) The Colour is changed by many gases. O makes blood scarlet, 

 want of renders it dark bluish-red, CO makes it cherry-red, NO 

 violet-red. There is no difference between the shape of corpuscles in 

 arterial and venous blood, as was supposed by Harless. All reagents 

 (e.g. f a concentrated solution of sodic sulphate), which cause great 

 shrinking of the coloured corpuscles, produce a very bright scarlet or 

 brick-red colour (Bartholinus, 1661). The red colour so produced 

 is quite different from the scarlet-red of arterial blood. Reagents 

 which render blood-corpuscles globular darken the blood, e.g., water. 

 [The contrast is very striking, if we compare blood to which a 1 per 

 cent, solution of common salt has been added with blood to which 

 water has been added. With reflected light the one is bright-red, 

 and the other a very dark deep crimson, almost black.] 



(b.) Change of Position and Form. A very common phenomenon 

 in shed blood is the tendency of the corpuscles to run into rouleaux 

 (Fig. 1, A, 3). 



Conditions that increase the coagulability of the blood favour this phenomenon, 

 which is ascribed by Dogiel to the attraction of the discs and the formation of a 

 sticky substance. [The cause of the arrangement of the red corpuscles into 

 rouleaux is by no means clear. They may be detached from each other by gently 

 touching the cover-glass, but the rouleaux may reform. Lister suggested that 

 the surfaces of the corpuscles were so altered that they became adhesive, and thus 

 cohered. Norris has made some ingenious experiments with corks weighted with 

 tacks or pins, so as to produce partial submersion of the cork discs. These discs 

 rapidly cohere, owing to capillarity, and form rouleaux. If the discs be com- 

 pletely submerged they remain apart, as occurs with unaltered blood-corpuscles 

 within the blood-vessels. If, however, the corpuscles be dipped in petroleum, 

 and then placed in water, rouleaux are formed]. If reagents which cause the 

 corpuscles to swell up be added to the blood, the corpuscles become globular and 

 the rouleaux break up. According to E. Weber and Suchard, the uniting medium 

 is not fibrin (although it may sometimes assume a fibrous form), but belongs to the 

 peripheral layer of the corpuscles. 



(c.) The Changes of Form which, after blood is shed, the red corpuscles 

 undergo until they are gradually dissolved, are important. Some reagents 

 rapidly produce this series of events e.g., the discharge of a Leyden jar 

 causes the corpuscles to crenate, so that their surfaces are beset with 

 large or small projections (Fig. 4, c, d, e, g, ti)- } it also causes the corpuscles 

 to assume a spherical form (i, i), when they are smaller than normal. 

 The corpuscles so altered are sticky, and run together like drops of oil, 



