THE BLOOD. 



crystals are said readily to appear in both cases ; but I must confess that 

 the second method has generally failed in my hands with human or bullock's 

 blood. The addition of alcohol, ether, and especially chloroform, greatly 

 promotes the operation. 



From human blood, and that of most mammals, the crystals are pris- 

 matic in form (fig. xix., 1 ), but tetrahedral in the guineapig, rat, and 

 mouse ( 2 ), hexagonal plates in the squirrel ( 3 ), and rhombohedrons in the 

 hamster ( 4 ).* 



Fig. XIX. The crystallising matter is perhaps modi- 



fied in its properties under these different 

 forms ; at least, it has been found that all 

 are not equally soluble in water. The red 

 colouring principle (haematin) is not essen- 

 tial to the crystals, for Lehmann has, by 

 i-ecrystallisation, obtained them free from 

 colour, and apparently unchanged in other 

 respects; neither does the undissolved 

 envelope or tegumentary frame of the 

 corpuscle take any share in the crystallisa- 

 tion. The crystallising matter, therefore, 

 must be the colourless protein-substance of 

 the cruor, namely, globulin. It has been 

 proposed to call this substance "blood- 

 crystalline," on account of its property of 

 crystallising, which does not belong to the 

 globulin of the crystalline lens, so far as is 



>i r \^ y e ^ known. The change of name, however, 



^^^fi is confusing, and appears inexpedient, espe- 



"^^J v^ cially as we know that all forms of globulin 



\/ agree in the much more characteristic pro- 



perty of being fibrino plastic. 



The haematin itself, or some chemical 

 modification of it, can also, it is supposed.be 

 crystallised; and the rhombic prisms and 

 acicular crystals (hcemin crystals), obtained 



by Teichmann by treating blood with concentrated acetic acid, are considered to be 

 of this nature. Crystals, moreover, of a substance (also occurring amorphously) which 

 has been named "haematoidin," and is probably derived from modified heematin, are 

 often found in old coagula and effusions of blood within the body. These occur in 

 form of rhombic plates or prisms, of a yellow or red colour; they are insoluble in 

 water, alcohol, ether, and acetic acid, and contain no iron. 



Fig. XIX. BLOOD-CKYSTALS MAGNIFIED. 



1, from human blood ; 2, from the 

 guineapig ; 3, squirrel ; 4, hamster. 



Proportion of red Corpuscles. The red corpuscles form by far the largest 

 part of the organic matter in the blood : their proportion may be ascer- 

 tained by filtering defibrinated blood mixed with solution of Glauber's salt, 

 as already mentioned ; or by weighing the dried clot, and making allow- 

 ance for the fibrin it contains. The latter method, however, will serve 

 only to give a rough estimate, as the very uncertain amount of serum 

 remaining in the clot and affecting its weight cannot be determined. 

 Prevost and Dumas made too large a deduction for the solid matter sup- 

 posed to belong to the retained serum, and this reduced the estimate of 



* A late writer, Bojanowski, represents them as rectangular tables in man and 

 hexagonal plates in the mouse. Zeitsch. f. Wissensch. Zool. 1862. 



