180 CIRCULATORY SYSTEM. 



SECT. III.' OF THE RED GLOBULES OF THE BLOOD. 



The particles of blood upon which its red colour depends are, 

 by a majority of observers, considered to be globular, and 

 while the blood circulates they float about in the lymph and 

 serum. They are of the same size in animals of the same spe- 

 cies, and have no tendency to run into each other, as globules 

 of mercury would. They are plastic, by which they can as- 

 sume an elliptical shape when they circulate through vessels 

 of a very small size. 



According to the microscopical observations of Mr. Bauer, 

 each globule is one two-thousandth part of an inch in diame- 

 ter, but Capt. Kater does not consider it to exceed one five 

 thousandth part of an inch.* There seems, however, to be a 

 great uncertainty in these estimates of form and of size, inas- 

 much as different observers do not agree among themselves. 

 Father Delia Torre considered them as flat circles or rings, 

 with a perforation in the centre, while Mr. Hewson, in 

 ascribing the same shape, represented them as hollow or vesi- 

 cular, with a red dot in the middle. Mr. Bauer, on the contra- 

 ry, considers that the dot, or colouring matter of the globule, 

 is placed upon its periphery. As the colour is supposed to de- 

 pend upon particles of iron, Dr. John Mason Good has wittily 

 suggested, that, according to Mr. Hewson, we have the wheels 

 of life moving upon iron axels, whereas, according to Mr. 

 Bauer, they only have iron tiers.t 



It has been observed that the red globules are the heaviest 

 part of the mass of blood, and are, therefore, always disposed to 

 subside to the bottom of the crassamenlum, though from the 

 quick coagulation of the latter, they can seldom do it before they 

 become entangled in it, and thereby fixed to a certain place. 

 They do not invariably retain their form, but are readily dis- 

 solved in water. They are, of course, insoluble in serum. Urine 

 does not dissolve them; neither does a solution of muriate of 

 soda, of sal ammoniac, Epsom salts, nitre, diluted sulphuric or 

 muriatic acid: the latter however, deprives them of colour. 



The solution of red globules in water is manifested by the mix- 



* Phil. Trans. 1818. t Study of Medicine, "vol, ii. p. 25. 



