212 MORBID STATES OF THE BLOOD, ETC. 



cellular substance — that the blood itself is a fluid. Its structural 

 elements are themselves of very unstable character. The blood 

 is rightly held to be that tissue whose losses are soonest remedied, 

 whose morphological and chemical constituents undergo on the 

 whole the most rapid change. We must recollect moreover, 

 that it does not elaborate its constituent elements within itself, 

 but draws its supply of cells from the lymphatic glands, the 

 spleen, and according to Bizzozero, Neumann^ and others, from 

 the marrow of bone, and its albumen from the alimentary canal. 

 In this resjDCct too therefore, certain determinate organs are 

 responsible for the composition of the blood. Accordingly the 

 blood is kept in its normal state by the systematic co-operation 

 of several factors ; by the due admixture and transformation of 

 its histogenetic elements ; by the uniform and easy supply and 

 removal of the more transitory nutrient and excrementitious 

 substances ; finally by the rigid exclusion of abnormal or 

 injurious matters from whatever source. Any irregularity in 

 these conditions alters the composition of the blood, and gives 

 rise to a dyscrasia; and indeed, the vast majority of blood- 

 diseases are nothing more than such morbid alterations of its 

 composition. 



§ 175. But few of the manifold dyscrasise of the blood admit 

 of being investigated anatomically; only those indeed which 

 depend upon morbid changes in the visible elements which are 

 suspended in the colourless liquor sanguinis. These elements are 

 usuallv distino-uished as : 



1. The red blood-corpuscles; flattened, biconcave discs, 

 about four times as broad as they are thick, without nuclei, 

 without a cell-membrane (?), made up of a colourless protoplasm 

 (stroma), and a reddish-yellow fluid material (haemato-crys- 

 tallin).* 



2. The colourless blood-corpuscles or leucocytes, which are 

 so rare in healthy human blood that for every 450 red cor- 

 puscles we find only one white one. These cells are destitute of 



* Besides the discoidal blood corpuscles we always find a certain 

 number wbicli have become spherical. These are characterised by their 

 apparent smalluess, and their darker, almost reddish-brown hue, 

 peculiarities readily explained by supposing that the same quantity of 

 matter which was previously spread out into a shallow disc, has shrunk 

 together to form a sphere. 



