iv THE BLOOD: FOEMED CONSTITUENTS 117 



based on the researches, first of Miescher and subsequently of 

 Hoppe - Seyler, on the. composition of pus. Pus cells, however, 

 are essentially composed of extravasated leucocytes which have 

 lost their vitality in great measure, or are on the way to dissolution. 

 They cannot, therefore, have the same chemical composition as 

 young and normal leucocytes. 



Lilienfeld has recently studied the chemical composition of the 

 leucocytes of the lymph (lymphocytes) which are richly distri- 

 buted in the reticulum of the lymphatic glands with interesting 

 'results. 



When a considerable quantity of lymph nodules previously 

 freed from fat and blood-vessels is put under pressure, a turbid 

 juice is yielded containing many well-preserved leucocytes, which 

 can be separated from the liquid by centrifuging. These readily 

 dissolve in water, and it is possible with magnesium sulphate to 

 obtain two globulins from the filtrate of the watery extract, one of 

 which coagulates at 73-75 C., the other, on the contrary, at 48 C. 

 If dilute acetic acid be added to the filtrate of the watery extract, a 

 phosphorus-containing substance belonging to the group of nucleo- 

 proteins, which Lilienfeld terms nucleo-histone, is precipitated, and 

 this is the principal constituent of the nucleus, not only in 

 leucocytes, but in other cells also. 



Nucleo-histone (which can be obtained pure, in the form of a 

 white powder, soluble in water) breaks up, on treatment with 

 baryta, or with dilute hydrochloric acid, or boiling water, into its 

 two component groups: a nuclein, which Lilienfeld calls leuco- 

 nuclein, and an albuinose, which, as we have seen, was in the first 

 instance extracted by Kossel from the nuclei of birds' erythrocy tes, 

 and which he called histone. 



On making an alcoholic extract from the mass of leucocytes 

 (obtained as above) it is found to contain protagon, lecithin, 

 cholesterin, inosit, and potassium phosphate. Fat is exhibited by 

 an ethereal extract. 



Besides these substances, leucocytes contain a small, constant 

 amount of glycogen (Hoppe-Seyler). 



According to Lilienfeld, the quantitative per cent composition 

 of leucocytes is as follows : 



Protein substances . . . . . . 1'76 



Leuconuclein 6878 



Histone 8-67 



Lecithin ......... 7*51 



Fat 4-02 



Cholesteriii ........ 4*40 



Glycogen . . . 0'80 



Nuclein bases (weighed as silver compounds) . . 15*17 



IX. The Blood-Platelets, which Bizzozero (1880) regarded as 

 the third formed element of the blood, had been previously 

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