MICROSCOPIC STRUCTURE OF THE BLOOD. 275 



yellowish or amber color, and the red color of the blood appears 

 only when the corpuscles are in thick layers or in masses. 



^Structure of Red Corpuscles. There is a difference of opinion 

 among histologists as to the minute structure of these bodies. 

 Schafer describes it as follows : " Each red corpuscle is formed 

 of two parts, a colored and a colorless, the former being a solution 

 of hemoglobin ; the latter, the so-called stroma, which is by far 

 the smaller quantity, being composed of various substances, chief 

 among these being lecithin and cholesterin, together with a small 

 amount of cell-globulin." According to this view, the colorless 

 stroma serves as an envelope to contain the hemoglobin in solution. 



By other authorities, of whom Rollett may be regarded as an 

 exponent, the entire corpuscle is made up of an elastic structure, 

 the stroma, the outer portion of which is denser than the inner, 

 and having in its interstices the coloring- matter together with 

 lecithin, cholesterin, and globulin. 



In discussing this subject, Gamgee, in Schafer's Text-Book of 

 Physiology, says : " Without attempting to speculate beyond the 

 facts which we possess, it may, however, be assumed that hemo- 

 globin exists in the blood-corpuscles in the form of a compound 

 with a yet unknown constituent of the corpuscle. This compound, 

 the existence of which we are forced to assume, is characterized by 

 remarkable instability, for it is decomposed, setting free the hemo- 

 globin, which then passes into solution (1) when the blood-plasma 

 or serum, in which the corpuscles are suspended, is diluted; (2) 

 when certain substances act upon the corpuscles (ether, chloro- 

 form, salts of the bile-acids, certain products of putrefaction) ; 

 (3) by the action of heat, by alternate freezing and thawing, by 

 induction shocks, etc." 



The red corpuscles are exceedingly flexible, as may readily be 

 seen by watching them in the circulation of the web of a frog's 

 foot. At times they will be so stretched out as to pass through a 

 vessel whose diameter is -smaller than is theirs when in a circular 

 shape ; or sometimes they may be seen bent over the projection 

 made by the junction of two vessels, one portion being within 

 each, until, one current being the stronger, they are carried for- 

 ward by it, resuming their circular shape as soon as the size of 

 the vessel permits. 



The human red corpuscles possess in adult life no nuclei. This 

 is true of all mammals. Up to the fourth month of fetal life the 

 blood of the human embryo contains nucleated red corpuscles. It 

 is uncertain, however, whether these develop into the non-nucleated 

 forms. In other vertebrates the corpuscles are nucleated. 



Chemical Composition of Red Corpuscles. An analysis of the 

 red corpuscles of human blood shows the presence of both organic 

 and inorganic compounds. The percentage of organic ingredients 

 in dried human corpuscles in one analysis was as follows : Proteids 



