24 The Farrier'j Ne'UJ Guide. Chap. VL 



thofe VeiTels had been of fuch a Texture, it would have 

 been impoflible for any animal Body to have been fup- 

 ported under the leall Diforder. But notwithftanding this 

 wife Contrivance, the Blood is ftill very liable to Obltruc- 

 tion whenever it happens to be too thick orvifcid. And 

 as all fuch Obflruciions muft rationally happen in thofe 

 Parts where the Vellels are of the fmalleit Texture, that 

 which flows in thofe that are larger, muft of Confequence 

 move with greater Rapidity ; becaufe^ as has been already 

 hinted, when it meets with Oppofition in its Courfe for- 

 wards, it muft deviate in greater than ordinary quantity, 

 and with greater Force, into the neareft lateral Branches. 



Nature furniflies us with few Similitudes that would be 

 of any Service to illuftrate this fort of Mechanifm, unlefs 

 a general Refemblance could be fufficient. Neither docs 

 Art aflift us otherwife than by Mathematical Experiments, 

 which v:ould not be cafily underftood but by thofe who 

 , . ^T r .> have feme infight into thcrn. But that this 



* i f.:f» i^iay be m.ade as plain as poiiible, we Ihall 

 ct: taken jiom J r i ■> _ 



Water runnivc fuppofe an Artery to be like a Fij^, which 

 in Pipesy Scc.^ giows giadually fmallcr, according to the 

 number of Branches it fends forth. We 

 muft alfo fuppofe this Pipe, and al! its Branches, to be 

 ronftantly filled with Water from fome Fountain, and this 

 Water perpetually runn'ng from the main Trunk into ail 

 thefe Branches : We muft in like manner imagine the Ex- 

 tremJties or Endings of thofe Branches to be fo fmall, as 

 to be cafily choak'd up with Sand or Clay, or any other 

 kind of Matter ; and therefore when any fuch Matter 

 happens totally, or in Part, to obftrucl: one or more of 

 thefe fmall Pafl'ages, the Water meeting with Refiftancc is 

 forced back again, and is taken up by thofe Branches that 

 are the neareft ; io the Branches, which are antecedent to 

 thofe that are thus obftru6ied, receive not only a more 

 than ordinary quantity of Water, but this Water is alfo 

 increafed in its motion in proportion to the Force by which 

 it is repuli'di and likewile by that of the Water, which is 

 antecedent to it, which being alfo in Motion, muft refift 

 its returning the fame way it came ; and, by giving a new 

 Impetus to the Water thus repulfed, muft drive it with the 

 greater Force into the lateral Branches. And this will 

 appear ftill more manifeft from the Inftance of a large 

 Stone throvv'n into a very fmall Brook or Rivulet, which 

 taking up fome Space, and dividing the Stream in the 



middle^ 



