THE RED BLOOD CORPUSCLES 189 



On examining the slide under the microscope, the crystals are seen singly or in 

 clusters. They appear as rhombic platelets and rods belonging to the monoclinic 

 system. In transmitted light they possess a mahogany-brown color, while in 

 direct illumination they exhibit a dark bluish tint. They are insoluble in water, 

 alcohol, ether and chloroform, but soluble in dilute alkalies. 



Hematoporphyrin differs from hemochromogen and hematin in that it contains 

 no iron. Nencki 1 gives its composition as C^Hss^Oe = 2Ci7Hi 9 N 2 O 3 . It is 

 prepared by adding crystallized hemin to a saturated solution of hydrobromic acid 

 in glacial acetic acid. Having permitted this mixture to stand for three or four 

 days, it is shaken with distilled water and filtered. The hematoporphyrin is then 

 thrown down by carefully neutralizing with caustic soda. It is insoluble in water 

 but soluble in acids, alkalies and ethyl alcohol. It appears as a dark, violet powder. 



The fact that hematoporphyrin is free from iron is of general interest in so far as 

 the bile pigments are also iron-free derivatives of hemoglobin; indeed, bilirubin 

 and biliverdin are commonly regarded as excretory products derived from hemo- 

 globin. The former pigment is isomeric with hematoporphyrin and both yield 

 on oxidation acids which are identical with those obtained from hematin. In this 

 connection, it should also be mentioned that the decomposition of stagnated blood, 

 as for example that of hemorrhagic extravasations into the brain, gives rise to a red 

 pigment, called hematoidin (Ca^HaeN^e) which is also free from iron and crystal- 

 lizes in clinorhombic prisms. This body is said to be identical with the biliary 

 pigment bilirubin and to be isomeric with hematoporphyrin. By abstracting one 

 molecule of oxygen from the latter, a body, called mesoporphyrin, has recently 

 been produced, which is said to possess the same composition as hematoidin. 

 Traces of hematoporphyrin are generally present in the urine; greater amounts of 

 it appear in certain types of poisoning. Crystals of hematoidin have also been 

 found in the urine after transfusion of blood and during icterus, when there is a 

 marked destruction of red cells. Of general interest is the fact that the green color- 

 ing matter of plants, known as chlorophyl, possesses a chemical structure similar 

 to that of hemoglobin. It may be inferred, therefore, that these bodies are closely 

 related to one another. This is shown, moreover, by the fact that hematoporphyrin 

 may be reduced to the oxygen-free hemopyrrol which is methylprophlpyrrol. In 

 a similar way, chlorophyl may be made to yield phylloporphyrin, a body closely 

 allied to hematoporphyrin which in turn may be changed into hemopyrrol. 2 



CLINICAL METHODS FOR THE DETERMINATION OF HEMOGLOBIN 



The hemoglobin content of the blood varies very slightly under 

 normal conditions, but fluctuates considerably in disease. Two fac- 

 tors may be held responsible for this inconstancy, namely, a change 

 in the number of the red cells or a change in their capacity to carry 

 hemoglobin. While these changes may arise independently of one 

 another, they are more frequently found to be associated with one 

 another. In the second place, it should be remembered that they 

 need not pursue a perfectly parallel course, because it frequently 

 happens that a reduction in the hemoglobin content is associated with 

 an increase in the number of the red cells. Conversely, a decrease in 

 their number cannot justly be regarded as a certain indication of a 

 loss in the total amount of hemoglobin, because the individual corpus- 

 cles may contain larger amounts of it. 



1 Monatshefte fur Chemie, x, 1889, 568; and Zeitschr. fur physiol. Chemie, 

 xxx, 1900, 384. 



2 Nencki and Marchlewski, Ber. der chem. Gesellsch., xxxiv, 1901. 



