Chemical Constituents of the Animal Body. 257 



pounds with oxygen (oxyhasmoglobin) and carbon-monoxide, 

 and by reason of their capacity to form the first-named 

 compound, they perform an important function in effecting 

 the oxygen supply to the tissues in the organism. 



Oxyhsemoglobin can be obtained in a crystalline form 

 by treating the corpuscles with water containing ether, 

 which causes them to " lake " that is, the cells are broken 

 up, and the contents escape. From the solution thus 

 obtained the oxyhaemoglobin separates in a crystalline 

 form on treatment with alcohol and cooling to between 

 5 and 10. On treatment with alcohol, ether, and 

 sulphuric acid, the oxy hemoglobin can be decomposed, the 

 globin being precipitated, whilst the pigment remains dis- 

 solved in the mixture of alcohol, ether, and water. 



The pigment can be separated in a crystalline form by 

 treatment of oxyhaemoglobin with hot glacial acetic acid, 

 which contains some sodium chloride. A product known 

 as haemin is thereby obtained, the composition of which, 

 according to the latest researches, can be represented by 

 the formula C 33 H 32 4 N 4 FeCl. This is a derivative of a 

 substance aetioporphyrin, C 31 H 36 4 N 4 , from which chloro- 

 phyll, the green pigments of plants, is also derived. This 

 interesting biological fact has been recently demonstrated 

 by Willstatter and his collaborators, who have described 

 their investigations in a monograph (" Untersuchungen iiber 

 Chlorophyll." Berlin, 1913). Aetioporphyrin is a some- 

 what complex substance, containing four pyrrol rings, of 

 which the constitution has not yet been definitely estab- 

 lished. Allied chemically to the blood pigment are the bile 

 pigments, bilirubin and biliverdin. All these substances 

 have been the subjects of numerous researches in recent 

 years, but the knowledge of them is not yet sufficiently 

 complete for a co- relationship to be established between 

 their chemical constitution and biological functions. 



(1,997) 17 



