210 STRUCTURE OF THE COLOURED BLOOD CORPUSCLES. 



Structure of the coloured blood corpuscle. Each red corpuscle is formed 

 of two parts, a coloured and a colourless, the former being a solution of hemoglobin, 

 the latter, the so-called stroma, which is in by far the smaller quantity, being com- 

 posed of various substances, chief among these being lecithin and cholesterin, together 

 with a small amount of cell-globulin (Halliburton and Friend). Water constitutes 

 about two-thirds of the corpuscles ; if the water is driven off, about 90 per cent, of 

 the residue is haemoglobin. 



If water be added to a preparation of blood under the microscope, the water is 

 imbibed and the concave sides of the corpuscle become bulged out so that it is 

 rendered globular. By the further action of the water the haemoglobin is dissolved 



Fig. 242. a-e, successive effects of water upon a red blood- 

 corpuscle ; a, corpuscle seen edgeways, slightly swollen ; b, c, one 

 of the sides bulged out (cup form) ; d, spherical form ; e, decolorized 

 stroma ; /, a thorn-apple shaped corpuscle (due to exposure) ; 

 g, action of tannin upon a red corpuscle. 



out of the corpuscle, and the colourless part or stroma 

 remains as a faint circular outline. This simple ex- 

 periment conclusively shows that the corpuscle is composed of a membrane or 

 external envelope with coloured fluid contents, for the above reaction 

 is precisely the same as would occur by osmosis with a bladder of the shape 

 of the corpuscle filled with a strong solution of albuminous substance and placed 

 in water (Schwann). On the other hand it is entirely inexplicable on the sup- 

 position that the corpuscle is composed of a uniform disc-shaped stroma, permeated 

 with coloured substance, which is the view advocated by Bruecke and Eollett, and 

 adopted by nearly all subsequent writers on the subject, for if this were the case 

 water should swell it out uniformly ; as happens if a disc of gelatine is placed in 

 water, the whole disc imbibing the water, and become increased in size but retaining 

 its original shape. 



The same fact is illustrated by the effects of mechanical injuries. If the 

 corpuscles are suddenly pressed they become ruptured and the haemoglobin escapes, 

 leaving the colourless part of the corpuscle as a mere outline. If blood is frozen 

 the ice-crystals which form rupture the envelope, and on thawing the haemoglobin 

 escapes into the serum. Electric shocks passed through blood, if sufficiently 

 strong, also rupture the delicate envelope of the corpuscles. Dilute acids 

 act like water, but decompose the haemoglobin into colourless proteid (globin) 

 and haematin, which are both dissolved by the acid. In the case of tannic acid, 

 the products of decomposition are usually precipitated upon the envelope in the 

 form of a small dark red coagulum (fig. 242, g}. Alkalies, even when very dilute, 

 cause a complete disappearance of the red corpuscles, the membranes as well as the 

 haemoglobin being dissolved : the latter is converted into alkaline haematin. Ether 

 or chloroform produce a similar effect when shaken up with blood, but may not 

 completely dissolve the envelope. The blood or serum of some animals produces 

 decolorization of the red corpuscles of others belonging to different genera. 

 This may be due to the fact that the one is more alkaline or of less specific- 

 gravity than the other, but the actual cause has not been determined definitely. 

 Solutions of common salt, if stronger than 0'6 per cent., produce when added to 

 blood crenation of the red corpuscles. This is due to exosmosis, the corpuscles 

 losing water and thereby becoming shrunken. Under like circumstances the blood- 

 corpuscles of the frog and newt, which do not exhibit crenation, show a wrinkled 

 appearance of the surface of the corpuscle, a phenomenon which is scarcely explicable 

 except by assuming the presence of a membrane. 



The action of ether and chloroform and that of alkalies seems to throw some 



