OF THE BLOOD AND CIBCTJLATION. 



195 



coidal (fig. 208, A), and vary between the 300th to the 400th 

 of a line in diameter. They are rarely seen either larger or 

 smaller. That they are flat, disc-like bodies, is discovered by 

 examining them on different sides. At the beginning of an 

 observation, before the drop has spread itself abroad com- 

 pletely, and the globules have come to rest, or at any time 

 when the port-object is inclined a little one way or another, 

 numbers of them are always seen on their edges (A, 6), when 

 they appear as long-shaped bodies, bounded by two parallel 

 lines. They are also seen falling, or rolling over (*), and with 

 everything at rest, finally sinking down upon their flat sides (a). 

 The blood-discs are severally so pale in colour, and so transpa- 

 rent, that when one lies over another, the undermost is seen 

 distinctly shining through the uppermost (a inferiorly). If 

 quite normal, a delicate semicircular shadow upon the flat sur- 

 face gives the observer the idea that the blood- discs are very 

 slightly hollowed out, or sunk, in the manner of a concave 

 lens. In a short time, sometimes after the lapse of a few se- 

 conds only, particularly when the diluting medium has not 

 been well selected, though it also happens from the action of 

 the air, the blood-discs begin to suffer change ; they appear 

 puckered and uneven ; they acquire notched edges, and are 

 stellated ; they seem to be made up of very minute globules, 

 or they look like mulberries or raspberries (C). The blood- 

 discs seem to have a natural tendency to approximate by their 

 flat surfaces, and go to form columns such as are produced by 

 pieces of money piled one upon another (B). 



[ 352. It is a matter of interest to compare the blood-cor- 



\S 



o 



V 



Fig. 209. Blood 

 globules of the com- 

 mon goat (Capra 

 domes tied). 



B 



Fig. 210. A, blood and lymph globules of 

 the pigeon (Columbadomesticaj. B, a blood- 

 globule, treated with diluted acetic acid ; C, 

 with water, by which the central nucleus be- 

 comes visible. 



o 2 



