THE YOUNG 



NATURALIST. 



135 



when stasis of blood occurs (Quain's Anato- 

 my, vol. ii, p. 25). 



Each corpuscle is made up of stroma and 

 haemoglobin, the former composing the 

 colourless and the latter the coloured 

 portion. The haemoglobin is readily soluble 

 in water, and may be separated from the 

 blood by shaking it up with this liquid, the 

 blood then loses its opaqueness and becomes 

 of a transparent and laky tint. The stroma 

 which constitutes the basis of the corpuscles 

 is proteid in nature and is chiefly made up 

 of globulin, lecithin, cholesterin and fats, 

 descriptions of which may be found in any 

 work on Physiological Chemistry (Ralfe 

 Gamgee, etc.) The colouring matter or 

 haemoglobin on the other hand presents 

 certain peculiarities which must be briefly 

 noted here. It exists in two forms — oxy- 

 haemoglobin or the haemoglobin of arterial 

 blood, and reduced haemoglobin or the 

 haemoglobin of venous blood. The former 

 which performs the great function in 

 animal life of carrying oxygen to the tissues 

 and restoring their vitality lost in doing the 

 work they were specially designed to do — 

 in muscle as contraction, in gland as secre- 

 tion, etc. — is of exceedingly great chemical 

 complexity. Its percentage composition is 

 given by Dr. Gerald Yeo as : — 



Carbon 53"85 



Hydrogen 7-32 



Netrogen 16-17 



Oxygen 21-84 



Sulphur "39 



Iron -43 



Curious to remark, oxyhaemoglobin, al- 

 though consisting in part of a colloidal 

 substance, when removed from the stroma, 

 crystallizes in almost all vertebrates, the 

 crystals occurring in the blood of man as 

 four-sided prisms or rhombohedral tablets, 

 in the squirrel as hexagonal plates, in the 

 guinea-pig as tetrahedrons, and in the ham- 

 ster as short rhombohedrons. Crystalliza- 

 tion occurs sooner in some animals than in 



others, as may be seen by the following 

 table :— 



Very difficult. — Calf, pig, pigeon, sheep, 



cow, frog. 

 Difficult. — Man, ape, rabbit. 

 Easy. — Cat, dog, mouse, horse. 

 Very easy. — Rat, guinea-pig. 



Examined with the spectroscope, oxy- 

 haemoglobin will be found to present two 

 absorption bands between the lines D and 

 E of Frauenhofer's lines, occupying the 

 position of the orange and yellow portions 

 of the solar spectrum. If the oxygen be 

 removed from the oxy-haemoglobin by the 

 influence of a vacuum, and so becoming 

 reduced haemoglobin, the double absorption 

 band is replaced by a single band with ill- 

 defined edges situated opposite the interval 

 between them. Haematin, or the colouring 

 principle of haemoglobin, in its turn appears 

 from recent research to be composed of 

 complex proximate principles ; and although 

 we are still partly in the dark concerning 

 their physical properties, their names and 

 chemical composition may be notified here : 

 they are — 



Methaemoglobin Unknown 



Oxy-haematin C 68 H 70 N 8 Fe 2 O l0 



Hsemochromogen . . . .C 34 H 36 N 5 Fe 3 0 3 

 Haematoporphyrin. . . .C 68 H 74 N 8 0 12 



Hsematolin C 68 H 73 N g 0 7 



Haematoidin C 32 H 36 N 4 O a 



Having thus considered the microscopic 

 and chemical peculiarities of the red blood 

 corpuscles, let us pass on now to the ques- 

 tion of their birthplace and their graveyard. 

 This has long haunted the minds of physi- 

 ologists, and many theories have been ad- 

 vanced and speculations created to explain 

 the manner in which they are formed ; and 

 afterwards, when they have run their course 

 of function in carrying oxygen to the tissues, 

 disintegrated : but we are still living in the 

 reign of theory. In the early embryo, 

 microscopic examination have shown them 



