CHEMICAL BASIS OF THE ANIMAL BODY. 1301 



sorption band in the extreme violet, the greatest absorption 

 taking place between h and L. 



Although it is quite easy to obtain typical crystals under the 

 microscope from minute amounts of haemoglobin or hsematin, 

 their preparation on a large scale is somewhat tedious. 



The successful preparation of hsemin crystals from minute 

 quantities of haemoglobin or methaemoglobin is of the greatest 

 importance for medico-legal purposes, since they suffice, even 

 in the absence of all other confirmatory evidence, to establish 

 the nature of the material used in their preparation. In the 

 detection of blood-stains it is usual first to examine with a 

 spectroscope an aqueous solution of the colouring matter if it 

 can be obtained, for the characteristic absorption bands of oxy- 

 haemoglobin or methaemoglobin. In old stains the haemoglobin 

 is frequently decomposed, in which case it is insoluble in 

 water, and alkaline extracts must be made and examined for 

 the spectra characteristic of hsematin. The residues from the 

 spectroscopic examination are lastly used to prepare haemin 

 crystals, in final confirmation of the evidence previously 

 obtained. 



Using amyl-alcohol in the preparation of haemin crystals it is 

 stated that the crystals have the following composition 



(C 32 H 30 N 4 FeO 3 . HC1) 4 C 5 H 9 . OH. 



The group C 32 H 30 lSr 4 FeO 3 is regarded as the true haemin, Teichmann's 

 crystals consisting of C 32 H s0 N 4 FeO 3 . HC1. When the crystals thus 

 prepared are decomposed by caustic alkalis as in the ordinary method 

 for preparing hsematin from them, the haemin is supposed to take up 

 one molecule of water and yield haematin, C 32 H 3 JST 4 Fe0 4 . "By treating 

 this haematin with strong sulphuric acid, it loses its iron and uniting 

 with oxygen yields haematoporphyrin or iron-free haematin, C 32 H 32 IS T 4 5 , 

 which is however further regarded as derived by dehydration from 

 a true haematoporphyrin whose composition is C 16 H 18 N 2 3 . The latter 

 is thus identical in composition with bilirubin, whose formula is 

 undoubtedly C, 6 H 18 lSr 2 3 . This is regarded as affording the desired 

 chemical proof of the genetic relationship of the bile- and blood-pig- 

 ments, the derivation of the former from haematin being represented 

 as follows, C 32 H 32 N 4 Fe0 4 + 2H 2 - Fe = 2(C :6 H 18 N 2 3 ). 



12. Haematoporphyrin. C 32 H 36 N 4 6 (?). (Iron-free haema- 

 tin.) 



If haematin is dissolved in concentrated sulphuric acid it 

 yields a solution which, after filtration through asbestos, is of a 

 brilliant purple-red colour. By the action of the acid, the iron 

 is removed from the haematin and haematoporphyrin is formed. 

 If this solution is diluted with sulphuric acid it shews with 

 spectroscope two absorption bands of which one adjoins D to 

 the red side of this line, while the other is very strongly marked 



