36 PRESERVATION OF RED BLOOD-CORPUSCLES. 



action be continued for a still longer time, the blood coloring matter 

 eventually separates from the stroma (k), and the blood-plasma con- 

 sequently becomes reddened, while the stroma is recognizable only as 

 a faint shadow (i). The changes in shape described represent the 

 effects also of a number of other injurious agents causing dissolution 

 of the red blood-corpuscles. Thus, for instance, all of the changes in 

 shape can be observed also in putrid fluid. 



Influence of Heat. If a blood-preparation be heated upon a warm 

 stage the corpuscles will be seen to undergo remarkable changes in 

 shape when the temperature reaches 52 C. They become in part 

 globular, in part drawn out into the shape of a biscuit, at times per- 

 forated, or larger or smaller drops of the substance of the body are com- 

 pletely constricted off. and float about in the surrounding fluid. This 

 is an evidence that considerable degrees of heat destroy the histological 

 individuality of the corpuscles. If the temperature be high and its 

 influence long continued, the erythrocytes are finally entirely dissolved. 

 In the case of burns the blood-corpuscles may undergo the same 

 changes within the vessels. 



The addition to blood of a concentrated solution of urea acts in the same 

 way as heat. Blood-corpuscles can be broken into fragments in microscopic 

 preparations by strong pressure. The disintegration of blood-corpuscles into frag- 

 ments may be designated erythrocytotrypsy, in contradistinction from their dis- 

 solution, which is known as erythrocytolysis. 



If a finger moistened with blood be passed over a hot glass plate so 

 that the thin layer of fluid is rapidly dried, the most remarkable forms 

 of long drawn-out distorted blood-corpuscles can be seen. This ex- 

 periment demonstrates in a striking manner their marked softness and 

 elasticity. 



If blood be mixed with a concentrated solution of mucilage and if, while being 

 examined under the microscope, concentrated solution of sodium chlorid is added, 

 the corpuscles become drawn out into longitudinal masses (dragon-shaped) . The 

 same change is observed if blood be admixed with an equal amount of liquid gela- 

 tin at a temperature of 36 C., and sections are made after the gelatinous mass 

 has hardened. 



PRESERVATION OF RED BLOOD-CORPUSCLES. 



The following are admirable preservative fluids for red blood-cor- 

 puscles : 



Pacini's Mixture. Hayem's Fluid. 



Mercuric chlorid, 2. Mercuric chlorid, 0.5. 



Sodium chlorid, 4. Sodium sulphate, 5. 



Glycerin, 26. Sodium chlorid, i. 



Distilled water, 226. Distilled water, 200. 

 To be diluted with two parts of dis- 

 tilled water before being used. 



In order to avoid all influence of the air in the examination of fresh 

 blood the following procedure is recommended: A drop of Pacini's fluid 

 is placed upon a portion of the skin, which is then punctured with a fine 

 needle through the fluid. In this way the blood rises into the preserva- 

 tive fluid without having at any time come in contact with the air and 

 the form of the corpuscles is at once fixed. 



In examining blood for medico-legal purposes the microscope is 

 naturally always employed. Dried spots are carefully softened by 



