74 COMPARATIVE ANATOMY 



ether. When separated, the haemoglobin crystallises out in 

 prisms. The haematids do not spontaneously alter their shape, 

 but they are very elastic, so that they can easily be squeezed 

 through passages smaller than themselves, and regain their 

 shape after the passage, as may be seen in the capillaries of 

 the frog's foot. 



The white corpuscles or leucocytes are much fewer in 

 number than the red, though their relative number varies con- 



ie* 



c* 



13- 



a, Red blood corpuscles (haematids) of the frog, stained with safranin and 

 much magnified, to show the nucleus and nuclear network, br, an 

 amoeboid coarsely granular leucocyte from the frog's blood, showing trifid 

 nucleus ; bz, bj, l>4, other forms of leucocyte from the frog's blood, c, 

 discoid non-nucleated haematids from human blood, much magnified ; 

 c/, C2, cj, different forms of leucocytes from human blood. 



siderably in different individuals, and in the same individual 

 at different times. A leucocyte, as it appears in freshly-drawn 

 frog's blood, when viewed under the microscope, is a minute 

 colourless body of smaller size than the red corpuscles, measur- 

 ing some o-o i 7 mm. in diameter. It consists, like the haematid, 

 of a protoplasmic body, containing a nucleus. The nucleus is 

 not easily seen in a living corpuscle, but it becomes apparent 

 on treatment with acetic acid, and it stains deeply with carmine 

 and other colouring, matters, whilst the protoplasmic body is 



