THE CIRCULATING LIQUIDS OF THE BODY 47 



haemoglobin in the methaemoglobin molecule than in the quantity 

 of oxygen which it contains. For methaemoglobin, unlike oxy- 

 haemoglobin, parts with no oxygen to the vacuum, while, on the 

 other hand, in the presence of reducing agents it yields up its oxygen 

 even more readily than oxyhaemoglobin does (Haldane) (p. 251). 



By the action of acids or alkalies oxyhaemoglobin is split into 

 a pigment, haematin and protein bodies, of which much the most 

 important is globin, a substance belonging to the histon group. It 

 is easily precipitated from solution by ammonia. As to the pig- 

 ment moiety, when haemoglobin is acted on by acids in the absence 

 of oxygen, hcsmochromogen is first formed, which then gradually 

 loses its iron and is changed into haematoporphyrin. If oxygen be 

 present, haematin is the final product. By the action of alkalies 

 reduced haemoglobin yields haemochromogen, which is stable in alkaline 

 solution, and gives a beautiful spectrum with two bands, bearing 

 some resemblance to those of oxyhaemoglobin, but placed nearer 

 the violet end. The band next the red end is much sharper than 

 the other (p. 68). 



Hcsmatin, the most frequent result of the splitting up of haemo- 

 globin, is generally obtained as an amorphous substance with a 

 bluish-black colour and a metallic lustre, insoluble in water, but 

 soluble in dilute alkalies and acids, or in alcohol containing them. 

 In addition to the iron of the haemoglobin, haematin contains the 

 four chief elements of proteins carbon, hydrogen, nitrogen, and 

 oxygen (Practical Exercises, pp. 67, 68). 



Hcematoporphyrin, or iron-free haematin, may be obtained from 

 blood or haemoglobin by the action of strong sulphuric acid. Its 

 spectrum in acid solution shows two bands, one just to the left of D, 

 the other about midway between D and E. Like oxyhaemoglobin, re- 

 duced haemoglobin, carbonic oxide haemoglobin, methaemoglobin and 

 other derivatives of haemoglobin, it also has a band in the ultra-violet. 



Hcemin is a compound of haematin and hydrochloric acid, which 

 crystallizes in the form of small rhombic plates, of a brownish or 

 brownish-black colour (Fig. 16, p. 67). They are insoluble in water, 

 but readily soluble in dilute alkalies (Practical Exercises, p. 71). 



Chemistry of the White Blood-corpuscles. The composition of 

 pus-cells and the leucocytes of lymphatic glands has alone been 

 investigated. The chief constituents of the latter are a globulin 

 coagulating by heat at 48 to 50 C. ; a nucleo-protein coagulating 

 in 5 per cent, magnesium sulphate solution at 75 C., and causing 

 coagulation of the blood on injection into the veins of rabbits; an 

 albumin coagulating at 73 C. ; and a ferment with powers like the 

 pepsin of the gastric juice. In pus-cells glycogen has been found, 

 and it can be demonstrated microchemically in the leucocytes of 

 blood by the iodine reaction in various conditions. Fats, cholesterin, 

 and lecithin are also present, as well as the so-called protagon. The 

 ordinary inorganic constituents have been demonstrated namely, 

 potassium, sodium, calcium, magnesium, and iron, united with chlorine 

 and phosphoric acid. The total solids amount to n to 12 per cent. 



The Quantity of Blood. The quantity of blood in an animal 

 is most accurately determined by the method of Welcker. The 

 animal is bled from the carotid into a weighed flask. When blood 

 has ceased to flow the vessels are washed out with water or physio- 

 logical saline solution, and the last traces of blood are removed 

 by chopping up the body, after the intestinal contents have been 



