188 THE BLOOD. 



farbig and lackfarbig, as applicable to the former and the 

 latter respectively. Blood ma}^ be rendered transparent or 

 laky by exposing it either to extreme cold or to a temperature 

 a little above GO C. ; b}^ subjecting it to the action either of 

 induced currents or of shocks of frictional electricity. A 

 similar effect, as already stated, is produced by the addition of 

 water and of various other liquid reagents, such as ether, chlo- 

 roform, and solutions of the bile acids in combination with 

 alkaline bases. 



11. Action of Cold. A platinum capsule containing a 

 couple of cubic centimetres of defibrinated blood is exposed 

 to a temperature of 6 to 10 C., 1 by placing it in a vessel 

 previously filled with alternate layers of pounded ice and salt, 

 and leaving it in contact with the freezing mixture until it is 

 completely frozen through. The solid mass of blood is then 

 slowly thawed and poured into a beaker, which should be of 

 such size that the blood contained in it is not more than half 

 an inch deep. If readily crystallizable blood has been em- 

 ployed, as, for example, that of the guineapig, a sediment of 

 crystals forms on the bottom. It is seen from the first that 

 the freezing has completely altered its appearance. It has 

 become darker in color, and if we place some of it on the sur- 

 face of a white plate with a pattern on it, the pattern is visible 

 with more or less distinctness through it, whereas if ordinary 

 blood were employed it would be completely concealed. It 

 is scarcel3 r necessary to add that the ciystallization is depend- 

 ent on the discharge of the haemoglobin from the corpuscles 

 into the liquor sanguinis. 



12. Action of Heat. (Method of Max Schultzc.) This 

 is a method which is only applicable to small quantities of 

 blood. In experiments with the warm stage {see Chap. I., p. 

 22). Max Schultze found that when blood is heated from GO 

 C. to 64 C., the blood corpuscles dissolve in the plasma. 

 The same effect is produced if a small quantity of blood is 

 subjected to similar temperatures in a hot chamber, furnished 

 with Bunsen's regulator. Here, as in the former case, if the 

 blood is derived from an animal in which the haemoglobin 

 crystallizes readily, crystals are obtained. According to 

 Preyer, remarkably fine crystals of haemoglobin may be pre- 

 pared by warming the colored corpuscles separated by subsi- 

 dence and decantation from the defibrinated blood of the 

 horse, in the manner above described. To insure success, 

 care must be taken to maintain the temperature of the quan- 



1 The effect of subjecting blood to the temperature of a freezing mix- 

 ture was first studied by Hewson. His experiment was similar to that 

 described in the text. His purpose was to show that cold is not the 

 cause of coagulation. He was not aware that frozen blood loses its 

 opacity. 



