The Microscope. 167 



greatest staying powers within the interior of any organ. 

 Virchow errs certainly here in two ways. Hfematoidin is derived 

 directly from the decomposition of haemoglobin, and not from 

 hfematin, which is already a product of decomposition. Secondly, 

 the crystals found in the ovaries after the rupture of a grafian 

 vesicle are not hfematoidin, but a crystalline substance sui generi, 

 which is now known as lutein, and which has a crystalline form of its 

 ■own, as we shall show later on. 



Hcemin crystals are produced artificially, and as such are of the 

 highest interest ivhen we are called upon to prove the presence of 

 blood. I hold these hfemin-crystals to be simply a kind of haematin, 

 produced by the action of acetic acid upon the blood. 



MODE OF OBTAINING THE BLOOD CRYSTALS. 



The production of haemoglobin crystals is surrounded at times 

 with more or less difficulty. When we remember that haemoglobin 

 so readily decomposes, this need not be wondered at. Often we 

 succeed in obtaining these crystals in an impure state, and re-crys- 

 tallization is necessary. It is also difficult to filter a blood solution, 

 and we will often fail before we learn how to proceed in the matter 

 successfully. It requires, in short, experience to produce fine, large 

 ciystals, which depend vipon concentration of the solution, access of 

 air and proper temperature. Let us remember here once more, that 

 haemoglobin is not ready -formed in the blood current, except under 

 certain rare pathological conditions ; that it is conjugated there to an 

 alkali, and that, in order to obtain it crystallized, this combination 

 must be broken up. We also must remember that this crystallizable 

 albuminoid is readily decomposed during the chemolysary process. 



Blood, to be manipulated to produce crystals, should be freed, 

 as far as possible, under loiv temperature, from serum and fibrin. 



The simplest means to dissolve blood is water. We allow the 

 blood to coagulate, express the serum, and the fibrin is separated by 

 filtration. Through this solution we direct a current of oxygen for 

 half an hour, then carbonic acid for ten or fifteen minutes. Crystals 

 are thus readily obtained from the blood of the guinea-pig, rat and 

 mouse. To obtain crystals from the blood of the dog and other 

 animals, alcohol in small quantities is added during the passage of 

 the gas currents. 



A second mode, employed by Kollett, is freezing of the blood, 

 which is previously freed of its fibrin by beating with small twigs. 

 Half an hour exposure to a freezing temperature suffices. We set 

 the frozen mass aside in a cool place and allow it to crystallize for 



