55 



is distinguished from these pigments by the fact that it contains no 

 iron. When strong sulphuric acid is allowed to act on blood or haemo- 

 globin solution, haematoporphyrin is also produced, as may be easily 

 shown by the spectroscope. Its spectrum in acid solution shows two 

 bands, one just to the left of D, the other about midway between D 

 and E. Like oxyhsemoglobin, reduced haemoglobin, carbonic oxide 

 haemoglobin, methaemoglobin, and other derivatives of haemoglobin, 

 it also has a band in the ultra-violet. 



Hamin (C 32 H 330^4. Fed) is readily obtained from haematin and 

 also from haemoglobin by heating with dilute hydrochloric acid, and also 

 directly from blood, as described in the Practical Exercises, p. 78. It 

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

 brownish-black colour (Fig. 24, p. 78). They are insoluble in water, 

 but readily soluble in dilute alkalies (Practical Exercises, p. 79). 



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 micro- 

 chemically in the leucocytes of blood by the iodine reaction in various 

 conditions. Fats, cholesterol, 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. 



SECTION IV. QUANTITY AND DISTRIBUTION OF THE BLOOD. 



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 physiological 

 saline solution, and the last traces of blood are removed by chopping 

 up the body, after the intestinal contents have been cleared away, 

 and extracting it with water. The extract and washings are mixed 

 and weighed ; a given quantity of the mixture is placed in a hasma- 

 tinometer (a glass trough with parallel sides, e.g.), and a weighed 

 quantity of the unmixed blood diluted in a similar vessel till the tint 

 is the same in both. From the amount of dilution required, the 

 quantity of blood in the watery solution can be calculated. This is 

 added to the amount of unmixed blood directly determined. Since 

 haemorrhage is immediately followed by the entrance of liquid into 

 the bloodvessels from the lymph and tissue fluids, somewhat too ; 

 high a result will be obtained if the bleeding is at all prolonged. T t 

 is well, therefore, to take only a moderate amount of blood for din 

 estimation, and to compute the balance by the colorimetric method. 



Many other methods have been devised on the principle of in- 

 jecting a known quantity of some substance into the circulating 

 blood, and then, after an interval has been allowed for mixture, 

 determining the change produced in a sample. Thus, the specific 



