152 THE BLOOD 



globin, but is more firmly united. There is also a compound of haemoglobin 

 which contains less oxygen than the oxyhaemoglobin, but is not completely 

 reduced like the haemoglobin. It is called pseudohcemo globin and has the 

 same absorption spectrum as haemoglobin (Siegfried). 



Haemoglobin unites with still other substances, as carbon monoxide (car- 

 bon-monoxide hcemoglobin) a compound corresponding to oxyhaemoglobin but 

 more stable, with carbon dioxide (carbon-dioxide hcemoglobin, cf. Chapter 

 IX) and nitric oxide (nitric-oxide hcemoglobin}. 



From analytical data Hiifner has calculated the following formula for the 

 hemoglobin of the dog's blood: C 636 H 1025 N 164 FeS 3 181 (molecular weight = 

 14,129). 



In different animals haemoglobin has a somewhat different constitution: for 

 the haemoglobin of the dog*, horse, swine, guinea pig, and squirrel various authors 

 have found the following constitution : C 51.2-54.9 per cent, H 6.8-7.4 per cent, 

 N" 16.1-17.9 per cent, S 0.39-0.86 per cent, Fe 0.34-0.59 per cent, O 19.5-23.4 

 p'er cent. 



For every molecule of haemoglobin contained in oxyhaemoglobin there is 

 one molecule of oxygen i. e., for 1 atom of iron, 2 atoms of oxygen. From 

 this it can be shown that 1 g. of haemoglobin can absorb 1.34 c.c. of oxygen. 

 The dependence of the oxygen absorption by haemoglobin upon partial pres- 

 sure will be discussed more fully in Chapter IX. 



Haemoglobin is a conjugated proteid (cf. page 75) in which a simple pro- 

 teid is coupled with an iron-containing pigment, hcemochromogen (Hoppe- 

 Seyler). In 100 parts of haemoglobin there are 94 parts proteid and 4 parts 

 coloring matter. The former consists for the most part of a histon-like basic 

 body, globin (Schulz), which like other simple proteids is laevorotatory, while 

 haemoglobin itself is dextrorotatory (Gamgee and Croft-Hill). 



On cleavage of haemoglobin, haemochromogen is formed, and by ab- 

 sorption of oxygen it passes over into licematin: C 34 H 34 5 N 4 Fe (Kiister), 

 C 34 H 35 5 N 5 Fe (Zeynek). By treatment of the blood pigment with HC1, 

 hcemin is obtained (Fig. 49): C 32 H 32 3 N" 4 FeCl (Nencki). 



Acids change haematin by loss of iron into the pigments mesoporphyrin, 

 C 16 H 18 2 N 2 (Nencki) and hcematoporphyrin, C 16 H 18 3 N 2 (Nencki). Ener- 

 getic reduction of the latter yields an oily, oxygen-free substance, hcemopyrrol, 

 C 8 H 13 N (Nencki), which according to Nencki and Zaleski is either an iso- 

 butyl pyrrol or a methyl-propyl pyrrol. 



Haematoporphyrin is only slightly different from a chlorophyll derivative, 

 phylloporphyrin C ir ,H 18 ON,, prepared by Schunk and Marchlewski. This fact 

 which indicates a close agreement between the structure of the most important 

 coloring matter of plants, and that of the most important coloring matter of 

 animals suggested to Nencki and Marchlewski the possibility of obtaining iden- 

 tical products from the two. They succeeded in producing hiemopyrrol from 

 chlorophyll. In view of the importance of pyrrol in the molecule of both haemo- 

 globin and chlorophyll, we may conclude that the two are in fact very closely 

 related. 



