144 METHODS FOR PREPARING, EXAMINING, AND MEASURING 



Our methods are briefly as follows: 



First method : The whole blood is laked and centrifugalized. If the 

 blood had been defibrinated, oxalate was added before centrifugalization. 



Second method : The corpuscles are separated by centrifugalization and 

 then laked, oxalate added to the solution, and the solution centrifugalized. 



Third method: The blood-clot is ground in sand, or the frozen clot 

 comminuted to liquefaction; the fluid thus obtained is laked, oxalate is 

 added, and then centrifugalized. 



Fourth method : In order to retard crystallization there may be added 

 to the blood, before or after laking, such inert substances as plasma, serum, 

 egg-white, water, glucose, gum, etc. The best results we have obtained by 

 the use of plasma, serum, or a 50 per cent solution of egg-white. This latter 

 is prepared by adding to the white of egg an equal volume of distilled water, 

 shaking violently in a flask for a few moments, and then straining through 

 linen. From 0.5 to 2 or more volumes may be added to the blood in accord- 

 ance with the effect required. The mixture is then centrifugalized until a 

 clear preparation is obtained. Occasionally the solution of egg-white was 

 clarified by agitation with ether and then by centrifugalization before it was 

 added to the already centrifugalized solutions of hemoglobin. Blood very 

 readily crystallizable will often be changed within a few minutes into a 

 magma of crystals, in which case excellent crystals can usually be obtained 

 by using the mother-liquor which has been separated by centrifugalization. 



When the blood is badly decomposed it is better to complete the laking 

 by repeated alternate freezing and thawing than by the addition of ether. 



The clear preparation obtained by these methods is placed upon 

 slides, and after the margins of the drops have become sufficiently dried 

 cover-glasses are put on, and in the course of an hour or two the covers 

 sealed with Canada balsam. 



The first method is especially adapted to bloods that crystallize readily, 

 such as those of Pisces and Marsupialia; the second, to those which do 

 not crystallize so readily, as those of Felidcc and Ungulaia; the third, to those 

 which crystallize with more or less difficulty, as those of Primates, Aves, and 

 Reptilia; and the fourth, to those which tend to crystallize so rapidly as to 

 yield crystals of too minute size, as those of Rodentia and Canidcc. Various 

 accessory incidental procedures will be referred to at the proper places. 



THE VALUE OF THE CRYSTALLOGRAPHIC METHOD OF INVESTIGATION. 



When a chemical compound solidifies from fusion, solution, or vapor 

 under conditions which are favorable to the development of individuals, 

 its particles tend to arrange themselves in regular order, so that a definite 

 structure is produced. The external form of the individuals is also regular, 

 being bounded by planes in definite relation to each other so that poly- 

 hedral solids are produced which are called crystals. The regular arrange- 

 ment of the atoms among themselves, and of the molecules which they 

 build up, is so characteristic of substances of definite composition that the 

 crystalline condition of dead matter is the normal condition. Differences of 

 chemical constitution are accompanied by differences of physical structure, 



