472 APPENDIX. 



lose first into a matter which is coloured blue by iodine, then into 

 sugar, and lastly into a humus-like substance. 



Composition. According to Mulder, the composition of this 

 substance is represented by the formula C 24 H 21 O 2l ; but according 

 to the more recent observations of Mitscherlich,* it is perfectly 

 isomeric with starch. 



Occurrence. Allusion has already been made to its occurrence 

 in certain of the lower animals. We can obtain cellulose in its 

 purest form from the pith or young roots of the elder by treating 

 them with various indifferent, as well as acid and alkaline solu- 

 tions, in order to remove any adhering soluble matter. Swedish 

 filtering paper is pure cellulose. 



(32) Addition to p. 314, line 10. The bilifulvin of Virchow 

 must not be confounded with the bilifulvin of Berzelius ; the former 

 seems to be identical with the haemato'idin also discovered by Virchow. 

 Virchowf found hsematoidin constantly present in the extravasated 

 blood consequent on the bursting of a Graafian vesicle in men- 

 struation or conception, and he often noticed it in old extravasa- 

 tions of blood in the brain, in obliterated veins, in hsemorrhagic in- 

 farctus of the spleen, in subcutaneous sugillations, and in abscesses 

 in the extremities. It appears from Virchow^s investigations, that 

 these crystals are formed in from 17 to 20 days after the extravas- 

 ation has occurred. 



Hcemato'idin occurs in an amorphous condition in granules, 

 globules, and jagged masses, as well as in perfect crystals belonging 

 to the monoclinic system. These crystals are oblique rhombic 

 prisms, not unlike crystals of gypsum : they often, however, occur 

 as nearly perfect rhombohedra (F. P. 6, F.3) ; they are strongly 

 refractive and transparent, of a yellowish red, red, or ruby-red 

 colour; they are insoluble in water, alcohol, ether, acetic acid, 

 dilute mineral acids and alkalies. I have on several occasions seen 

 the smaller and lighter-coloured crystals dissolve in alcohol con- 

 taining sulphuric acid or ammonia, and again precipitated by 

 ammonia ; this, however, is not always the case. Virchow 

 has accurately studied the behaviour of this body with con- 

 centrated alkalies and mineral .acids : these reagents, however, 

 do not seem to act uniformly on all specimens of haematoi- 

 din; on the addition of hydrated potash the pigment usually 

 assumes a glowing red tint, the mass gradually separating and 

 breaking up into red granules, which slowly dissolve ; the substance 



* Ber. d. Akad. d. Wiss. zu Berlin. 1850, S. 102-111. 

 t f Arch. f. path. Anat, Bd. 1, S. 383-445. 



