( r-4 ) 



to beftow flill more attention on it, by examining the hind feet of 

 many fmall live crabs. In one of thefe I faw, by the microfcope, 

 not only a large artery, about the fize of an hair, which, before it 

 came to the extremity of the foot, divided itfelf into leveral fmall 

 branches ; but I alfo faw a great number, both of arteries and 

 veins, croffing each other; and, on turning my eye a little towards the 

 fides of the foot, I there faw the blood poured into lb many minute 

 veflels, that the fubllance w hich we fliould call the tlelliy part of 

 the animal, lying between the Ikin or fliell of the foot, teemed 

 to confill of nothing but blood veflels; fo that when I Ihewed this 

 circulation of the blood to a certain learned phj'lician, he frequently 

 exclaimed, " O how wonderful is this !" 



The pleafure which this objed: afforded me was the greater, 

 becaufe the globules of blood, driven through all the vellels, being 

 fewer in number, were much wider afunder than the globules 

 in the blood of terreflrial or aquatic animals which are of a red 

 colour; fo that, I am well aflured, the globules in red blood 

 are twenty-five times more in number than thofe, in the fame fpace, 

 in the blood of a crab. 



After I had feveral times repeated my obfervations on thefe 

 minute crabs, and my fight was in a manner wearied with the 

 fpecflacle, however pleafing, I had a mind to fee the blood when 

 drawn out of the veflels, and the rather becaufe the ferum or fluid 

 in which the globules were fwimming, was fo very tranfparent, 

 that it would be impoflible to difcem the circulation without the 

 afliftance of thofe globules. 



The artery in this crab's foot was too fmall to be opened in the 

 ordinary way; I therefore determined to cut off a fmall part at the 

 extremity of the hind foot with a pair of fcifl"ars, and then to col- 

 led: the blood as it firil ifllied forth, and place it before the micro- 

 fcope. This being done, I faw in the fmall portion of blood 

 which iflued from the artery, the globules of blood for fome time 

 continue their circular motion. 



