ELEMENTARY PHYSIOLOGICAL CHEMISTRY 193 



Conditions which hasten Clotting. (1) Body temperature. 



(2) The addition of some clotted blood (clot or serum). 



(3) Agitation, e.g., whipping the blood with a bunch of twigs. 



(4) Contact with a rough surface. 



(5) Introrvitam methods. Certain conditions cause the blood to clot 

 within the blood-vessels. These are : 



(a) Injury or death of the blood-vessel wall, e.g., when an artery is 

 crushed, as in a contused or lacerated wound, a clot forms which acts as 

 a natural plug to prevent haemorrhage. When the arterial wall under- 

 goes degeneration, a clot, or thrombus may form. 



(fi) Rapid injection into a vein of a strong alkaline solution of nucleo- 

 proteid " positive phase" of nucleo-proteid injection. 



THE CHEMISTRY OF THE LEUCOCYTES. 



These are morphologically the same as other cells, and they contain 

 the same chemical substances. The protoplasm consists mainly of water. 

 The solids consist of various proteids, which chiefly belong to the 

 group of compound proteids (gluco-proteids and nucleo-proteids), and 

 there is also a small amount of albumin and globulin. The protoplasm 

 may also contain such substances as glycogen, fat, mucin, etc., which 

 have either been produced by the activity of the protoplasm, or which 

 are simply deposited in the cell for storage purposes. 



The nucleus seems to consist mainly of nucleo-proteids, nuclein and 

 nucleic acid. The nucleo-proteid of the nucleus is said to contain a 

 higher percentage of phosphorus than does that of the protoplasm. 



THE HAEMOCYTES OR RED BLOOD CORPUSCLES. 



Structurally these are said to consist of a stroma containing in its 

 meshes a peculiar proteid called Haemoglobin. It is, however, impossible 

 to demonstrate this stroma histologically, and the whole question of the 

 structure of haemocytes seems shrouded in mystery. 



Chemically they contain about 60 per cent, of water and nearly 36 

 per cent, of haemoglobin, the remaining 4 per cent. represented by 

 the so-called stroma consisting of lecithin, cholesterin and nucleo- 

 proteid. 



Haemoglobin. This is a compound proteid containing 0-4 per cent. 

 of iron. When decomposed by acids or alkalies it splits up into a- 

 proteid of the nature of a histon (see p. 178) called globin and into a pig- 

 ment called haematin, which contains all the iron. A pure solution of 

 haemoglobin can be obtained by centrifugalising defibrinated blood, 1 



1 Horses' blood should be used for this purpose as the corpuscles sink more 

 quickly than the corpuscles of any other blood do. 



