The Blood. 83 



posed to the air until it becomes brown in colour and acid 

 in reaction ; this substance gives a three-banded spectrum, 

 and parts from its oxygen with difficult}'. In Carbonic oxide 

 haemoglobin the haemoglobin is already saturated with CO, 

 and so cannot carry oxygen to the tissues, thereby rapidly 

 producing death. The blood of people who have died from 

 CO poisoning is of a cherry-red colour, and yields the 

 spectrum of CO haemoglobin — viz., two bands very much 

 like those of oxy- haemoglobin, but situated nearer to the 

 violet end of the spectrum. Nitric oxide haemoglobin in 

 many respects resembles CO haemoglobin. 



Haemoglobin may be decomposed either by boiling or the 

 addition of alkalies, acids, or acid salts ; in either case it 

 splits up into a substance containing all the iron of the 

 haemoglobin, and known as h3ematin, and a proteid sub- 

 stance or substances termed globin. 



Haematin has a metallic lustre, blue-black colour, is free 

 from crystalline formation, and yields a dark-brown powder 

 when pulverized ; it contains 8*82 per cent, of iron. 

 Haematin presents a distinctive spectrum, both in an acid 

 and alkaline solution. 



When haematin is boiled with glacial-acetic acid it yields 

 haemin, which, microscopically, is found to consist of prismatic 

 crystals, dark, or nearly black in colour. Hoppe-Seyler 

 considers this substance to be hydrochloride of haematin. 

 The ready production of hcemin crystals by warming the 

 blood with a drop of acetic acid on a slide is used as a 

 microscopical test. 



There are other derivatives of haematin, such as 

 Haemochromogen, which is a reduction product ; Haemato- 

 porphyrin, which is haematin from which the iron has been 

 removed ; Haematoidin, found in old blood-clots and in the 

 ovary, it is an iron free product of haematin, and gives the 

 same reaction with nitric acid as bile pigment, viz., a play 

 of colours. Haematoidin is, in fact, identical chemically 

 with bilirubin. 



The White Corpuscles, also termed leucocytes, are found 

 in blood, lymph, pus, connective tissue, etc. They exist in 



3 



