ADDITIONS AND NOTES TO VOL. I. 491 



been obtained. But is it not probable that all the protein-bodies, 

 or a substance separated from mineral matters and common 

 to all of them, may crystallise ? But even when crystals have 

 actually been obtained from an albuminous fluid, it requires a very 

 careful investigation to prove their identity with the crystalline 

 substance of the blood. 



Physiological relations. We have already remarked in the preced- 

 ing pages, that the crystallisable substance of the blood is limited 

 to the coloured blood -corpuscles, as Funkehas especially shown to 

 be the case. It would appear, however, from experiments made 

 on the subject, that it occurs in all red-blooded animals, although 

 it may present the various modifications which have already 

 been noticed ; it is also more readily obtained from certain kinds 

 of blood than from others. 



We must yet enter somewhat more circumstantially into the 

 mode of preparation of the crystallisable matter, since this subject 

 is one of importance, when considered in reference to many still 

 doubtful points referring to the blood. The blood-crystals are 

 formed from blood containing fibrin and serum, as well as from 

 blood which has been deprived of its fibrin, and possibly also 

 from cruor freed from serum. Under certain relations, they are 

 formed so rapidly and in such great quantities, that they frequently 

 appear where one would the least expect to meet with them. 

 Thus, for instance, they occur in great abundance whenever blood- 

 clots (as, for instance, from men, cats, and dogs) which have only 

 been roughly chopped, and which have been frequently although 

 imperfectly washed in water, are suffered to remain for some time 

 exposed in a moist state to the air, either in ordinary light, or, 

 what is better, in sunlight ; when thus treated, the superficial 

 parts of the pieces of fibrin are rapidly covered with entire crusts 

 of the most beautiful and large crystals. I obtained the tetrahedric 

 crystals, to which I have already referred, most rapidly, that is to 

 say, in 35 minutes after the animal had been killed, from the 

 blood of guinea-pigs; the defibrinated blood, after being diluted with 

 water and treated in the manner described in the preceding page 

 (an aqueous extract of the cruor may also be employed for this pur- 

 pose) is exposed for 15 minutes to a stream of oxygen either in 

 broad day-light or sun-light, and carbonic acid is then conducted 

 through the lighter red fluid for five, or at most ten minutes ; the 

 carbonic acid gradually renders the fluid darker, but it soon 

 becomes more and more turbid ; in accordance with the degree of its 

 turbidity, the fluid exhibits a more or less briaht vermilion red tint 



