COLOURLESS CORPUSCLES OF BLOOD. 131 



proportion of Red corpuscles, it is invariably accompanied by muscular de- 

 bility and deficient nervous power. 



a. By Liebig it is supposed, that the iron in the red corpuscles is the real agent in the 

 respiratory process : for if its original state be the protoxide, it may become the peroxide 

 by uniting with an additional atom of oxygen, or the protocarbonate by the addition of an. 

 atom of carbonic acid. The former change is supposed by him to take place in the lungs, 

 to which the blood comes charged with carbonic acid ; the carbonic acid is given up by the 

 iron, and replaced by an equivalent of oxygen taken in from the air : whilst in the syste- 

 mic capillaries, the converse change takes place, the oxygen being imparted to the tissues, 

 and being replaced by carbonic acid which is given up by them to be conveyed out of the 

 system. It is stated by Liebig that there is far more than sufficient iron in the whole mass 

 of the blood, to convey in this manner all the oxygen and carbonic acid, which are inter- 

 changed between the pulmonary and systemic capillaries. The speculation is certainly an 

 ingenious one ; but it can scarcely be yet received as a physiological fact. 



151. Besides the red particles of the Blood, there are others which possess 

 no colour, and which seem to have a function altogether different ; these are 

 known as the White or Colourless corpuscles. Their existence has long 

 been recognized in the blood of the lower Vertebrata, where, from being much 

 smaller than the red corpuscles, they could readily be distinguished. But it 

 is only of late, chiefly through the researches of Gulliver, Addison,* and 

 others, that they have been recognized in the blood of Man and other Mam- 

 malia ; their size being nearly the same with that of the red corpuscles; and 

 the general appearance of the two (owing to "the circular form of the latter, 

 and the absence of a proper nucleus,) being less distinct. It is remarkable 

 that, notwithstanding the great variations in the size of the red corpuscles in 

 the different classes of Vertebrata, the dimensions of the colourless corpuscles 

 are extremely constant throughout ; their diameter seldom being much greater 

 or less than l-3000th of an inch. This has been observed even in those ani- 

 mals, the Musk-deer, and the Proteus, which present the widest departure 

 from the general standard in the size of their red corpuscles : so that the 

 colourless corpuscle is as much as four times the diameter of the red, in one 

 instance ; whilst it is not one-eighth of the long diameter of the red, in the 

 other. Hence it would seem very improbable, that the red can never be con- 

 verted into the white, or the white into the red. The aspect of the two, under 

 the Microscope, is very different. Instead of presenting a distinct central 

 nucleus, like the red corpuscles of the Oviparous Vertebrata, or being en- 

 tirely destitute of granular contents, as are those of Mammalia when unaffected 

 by reagents, the colourless corpuscles are studded with minute granules, 

 which may be occasionally seen in active motion within them, and which are 

 discharged when the corpuscles are treated with liquor potassae. They pos- 

 sess, moreover, a higher refracting power than the red corpuscles ; and are 

 further distinguished from them, by their greater firmness, and by the ab- 

 sence of any disposition to adhere to each other ; so that, when a drop of recent 

 blood is placed between two strips of glass, and these are gently moved over 

 one another, the white corpuscles may be at once recognized by their soli- 

 tariness, in the midst of the rows and irregular masses formed by the aggre- 

 gation of the red. This is still better seen in inflamed blood ; in which the 

 Red corpuscles have a peculiar tendency to adhere to one another, whilst the 

 White are present in unusual number. 



152. The Colourless corpuscles may be readily distinguished in the cir- 

 culating Blood, in the capillaries of the Frog's foot ; and it is then observa- 

 ble, that they occupy the exterior of the current, where the motion of the fluid 

 is slow, whilst the red corpuscles move rapidly through the centre of the tube. 



* Transactions of the Provincial Medical Association, 1842 and 1843. 



