BLOOD. 



31 



Taking this drop of blood from my finger as a 

 standard of comparison, we find, on applying the mi- 

 crometer, that the disks rim from l-2500th to l-5000th 

 of an inch ; but that the great majority are about 

 l-3300th in diameter. On these slides are samples of 

 other kinds. This is the blood of a Fish, — the common 

 Blenny or Shanny {Blennius pholis). Here we see 

 at once the oval form of the disks ; their average is 

 l-2800th by l-3300th of an inch. Here is the blood of a 

 Frog {Rana, temforario) ; these are more than twice 

 the size of the fish's ; for they average l-1250th by 

 l-1800th of an inch. And, finally, I can show you a 

 drop of blood from this Smooth-newt {Lissotriton punc- 

 tatus). The large size of the disks is now conspicuous, 

 and so indeed is the elegance of their form : in this 

 case, as in the last, we see in each disk a distinct round- 

 ish nucleus. These run from l-YOOth to l-950th in 

 length, by 1-llOOth to l-1600th in breadth ; but the 

 average are about l-800th by l-1300th of an inch. 



a Man. 



BLOOD-DISKS. 



& Blenny. c Frog. 



(2 Newt. 



It may interest you to see these blood-disks in their 

 proper situation, and to observe the motion which 



