ALBUMINOUS COMPOUNDS. 65 



between the albuminous and gelatinous compounds. The undissolved residue 

 left when fibrin has been boiled for some time, to which the name of binoxide 

 of protein has been given, is soluble in dilute acetic, hydrochloric, nitric and 

 sulphuric acids, and also in potash and ammonia, and it is precipitated from its 

 acid solutions by ferrocyanide of potassium and acetate of lead ; in these re- 

 spects, therefore, agreeing with the protein-compounds. This substance also 

 seems to exist in the buffy coat of the blood, and perhaps too in healthy blood ; 

 but the chief interest attaching to it arises from the fact, that a substance appa- 

 rently identical may be obtained from Hair, by dissolving this in potash, adding 

 a little acetic acid to throw down the protein, and then adding a larger quantity of 

 the acid, which throws down the binoxide of protein as a bright yellow precipitate. 

 31. Although differing considerably from the protein-compounds in its che- 

 mical constitution, the Hsematin, which forms the coloring portion of the con- 

 tents of the red corpuscles of the blood, will be here most appropriately noticed ; 

 being obviously a derivative from albumen, and being not improbably in progress 

 of preparation to bear a part in the composition of higher tissues. Hsematin is 

 so intimately united with the Globulin of the red corpuscles ( 23), that the 

 two substances can only be separated after their solidification; what is said of 

 its properties, therefore, refers only to its coagulated state. It constitutes, when 

 dried, a dark brown, slightly lustrous mass, which is devoid of taste and smell, 

 and is insoluble in water, alcohol, and ether ; it is readily dissolved, however, 

 by weak alcohol to which sulphuric or hydrochloric acid has been added, and 

 forms a brown solution, which, on saturation with an alkali, yields a blood-red 

 color. Water acidulated with the same acids, exerts no solvent power on hae- 

 matin ; but very dilute solutions of the caustic alkalies or their carbonates, 

 either in water or in alcohol, dissolve hsematin in almost every proportion. In 

 ultimate composition, Haematin departs widely from either the albuminous or 

 the gelatinous type, and is remarkable for containing a considerable proportion 

 of iron ; as is seen Vy the following statement founded upon Mulder's analyses : 



Carbon. - . ' ,. ' . ? ''". ' _ V. "'"' "'' :^'/ ; V '"", , . 65.3 



Hydrogen . - . '''' '' 5.4 



Nitrogen . ; 'SV "* '. . . . . . . . 10.4 



Oxygen ,.. v '?!^ H- 9 



Iron 7.0 



100.0 



Much controversy has taken place regarding the condition in which the Iron 

 exists in Hsematin ; and the question cannot be regarded as yet satisfactorily 

 determined. This much, however, is certain; that the red color is not due, as 

 has been commonly supposed, to the presence of iron ; since it has been clearly 

 shown by Scherer, Sanson, and Mulder, that the iron may be abstracted from 

 this red pigment, by the agency of acids, without in the least degree affecting 

 its color. Of the mode in which Haematin is generated, and of its office in the 

 animal economy, we are at present completely ignorant. It would appear to 

 be formed by the agency of the blood-cells, at the expense of the components 

 of the fluid in which they float ; and it is considered probable by Lehmann, that 

 in this metamorphosis fatty matter takes an essential part. Hsematin does not 

 present itself normally anywhere else than in the red corpuscles; and although 

 there appears some reason to believe that these are specially connected with the 

 activity of the respiratory process ( 147), yet no direct evidence has yet been 

 obtained as to the mode in which they minister to it. 1 The color of muscular 



1 It may, however, be said with almost positive certainty, that the notion put forth by 

 Prof. Liebig that it is the iron of the blood-cells which serves as the carrier of oxygen 

 5 



