XXIII. 



Some /nMcroscopic ffrfenfcs, 



WHEN a very thin film of blood is placed under a 

 microscope of sufficient power, we observe that, so far 

 from being a uniformly red fluid, blood is really as 

 colourless as water. This apparent paradox between 

 what we see with the unassisted sight and what is be- 

 held under the microscope, is entirely explained when 

 we discover that the red colour of blood is due, not to 

 any inherent property of colour in blood a? a fluid, 

 but to the enormous number of red particles which 

 float in it. What the microscope enables us to see 

 is the clear liquid between the red particles it bears. 

 To the naked eye, which is unable to distinguish 

 minute objects, and which sees things only in the 

 mass, as it were, blood naturally appears red. In any 

 case, it will take its colour from its floating particles. 

 Some worms have green blood ; this is due to the 

 green hue of their blood-particles. An oyster or a 

 lobster has colourless blood, because it possesses no 

 coloured particles at all, but only white or colourless 

 ones. The blood-particles we name " corpuscles ; " 

 and in addition to the red ones seen in our blood 

 there are also white corpuscles. The latter are less 

 numerous than the red, and we may calculate that 

 about one white to 400 or 500 red corpuscles, is to 



