34 BLOOD CORPUSCLES. 



their amoeboid movements, assume the spheroidal form. Their 

 movements, however, are resumed as soon as the excitation is 

 discontinued. The motion is more undulating than before, 

 but soon recovers its former character. After repeated excita- 

 tion the corpuscles expand into lamina?, but still exhibit 

 changes of form. Under the influence of successive shocks of 

 greater intensity, the colorless corpuscles swell out, their 

 granules exhibiting molecular movement, and finally disappear. 



Blood Crystals. In concluding this chapter, we propose 

 to give the most simple methods of obtaining crystals of haemo- 

 globin and hoemin for microscopic purposes, referring the reader 

 for more detailed information to Chapter XV. 



Haemoglobin. A large drop of blood is taken directly 

 from a living guineapig, and allowed to coagulate on a watch- 

 glass. We now add a small quantity of water, and then, 

 taking up the clot witli the forceps, let fall on a glass slide 

 several small drops. As these drops evaporate hemoglobin 

 crystals of varying size shoot out from the edge, separately 

 and in bunches. 



Another plan is to cut out the heart and great vessels of a 

 recently killed guineapig, placing them on a watch-glass in 

 saturated air for twenty-four hours. Then take some blood 

 from the heart by means of a capillary tube, and allow a very 

 small drop to fall into an equally small drop of water on a 

 slide. As it evaporates, crystals are formed as before. This 

 method does not answer with rabbit's blood. 



Hssmin Crystals. The simplest method of obtaining 

 htcmin crystals is the following: A small quantity of dried 

 mammalian blood (human will do) is placed on a slide. A few 

 small crystals of common salt are then added, and a cover- 

 glass placed over. A drop of glacial acetic acid is then allowed 

 to enter from the side. On warming the preparation carefully 

 until the greater part of the acid has evaporated, an immense 

 number of the reddish-brown crystals of hsemin are seen. 



For a description of the corpuscles which occur in the lym- 

 phatic system, see the chapter treating of that subject. The 

 development of the blood corpuscles will be described in Chap- 

 ter VII. 



