THE BLOOD. 39 



Ammonia. This alkali acts in a similar manner. 



Nitric Acid, Muriate of Soda. These re-agents contract 

 the globules, and render their outlines more distinct. 



Iodine. This likewise renders the outlines more distinct, 

 without at the same time deforming and otherwise altering 

 the globules. 



Corrosive Sublimate. In a strong solution of this liquid, 

 the outlines of the globules are more defined, and the 

 globules may be preserved for examination for a considerable 

 length of time. 



We shall next pass to the consideration of the white glo- 

 bules, and show in what particulars of form and structure 

 they differ from the red. 



WHITE GLOBULES. 



The white globules of the blood are by far less numerous 

 than the red ; they nevertheless are more abundant than a 

 superficial observer would suppose : this arises from the fact 

 that many of them are concealed from view on the field of 

 the microscope by the red globules, which so greatly out- 

 number them. The white corpuscles differ from the red in 

 several particulars in size, in colour, in form, in structure, 

 in their properties, and doubtless also in their uses.* 



Size. In man and the mammalia the white globules are 

 generally larger than the red : like those, also, their dimen- 

 sions vary very considerably in the blood of the same indi- 

 vidual abstracted at any given time, and even to an extent 

 still greater. Their average size, when contained in the 

 serum of the blood, may, however, be estimated at about the 

 2jV(j of an inchf (see Plate I. Jig. 1.): when immersed in 

 water, however, they swell up, and increase very consider- 

 ably in size, in this liquid sometimes measuring the 



* Spallanzani was the first to notice the existence of two forms of 

 globules in the blood of salamanders ; Miiller verified their presence in 

 that of the frog, and M. Mandl detected them in man and mammalia. 



f Mr. Gulliver gives the ^'ov f an ^ ncn as tne average measurement 

 of the human colourless blood corpuscle. 



E 



