• C 305 ) 
have fometimes meet with PolHpufes very large,- but 
I never yet but found the Right Auricle and /v^enmcle to 
be furniflied with the largeft. 
Blackifli Urin , I believe is commoniy obferved in 
many Feverifli Indifpofitions ; where the Blood is ei- 
ther partially obftrud:ed in its return by the Veins of 
the Kidneys, or through its great Veilocity in pa/ling 
the Kidneys ; when Tome parts of the Globules of the 
Blood alfo paft out at the Urinary pores in the fides of 
the Blood Veflels, and thofe Globules being broken, ex- 
hibit thofe blackilh Bodies which appear in the Sedi- 
ment of the Urine. In ihefe Cafes the Serum of the 
Blood pafles off with the Urine ; for by evaporating 
iiich Urine by heat, as in a Spoon over a Candle it will 
Ididitk and become thick like the true Serum of the 
Blood, as it appeared in examining the blackiih Urine 
of a Child, in company of my Friend and Learned Phy- 
fician Dr. Hoy, Obftru6tions commonly begin in the 
moil: capilary Veffels firfr as I have frequently ob- 
ferved in viewing the tranfparent Finns of divers living 
Fiflies with my Mycrofcope : And tho' it has been hi- 
therto commonly fuppofed, that Veins and Arteries are 
all equally leflened at their extremities • yet I am of Q- 
pinion, (and I believe can give Ocular Dem.onftration of 
it too) that the extremities of divers Blood Veflels, are 
much larger than their Companions : Hence an Account 
may be given of the partial Circulation of the Blood, 
and yet Mortifications not necefTarily fucceed, as in the 
prefent Cafe : For the Kidney here being vafily exten- 
ded, which proceeded from a Retardation of the Re- 
fluent Blood and Lympha ; it is conceivable that the Ob- 
11 rudlions began in the Membranes, which compofe the 
Parities of the Trunks of the Veins and Limpheduds, 
whence an Intumefcence neceilarily follows ; and the 
Cavities of thofe Veiicls are kflened, coiifequently the 
Refluent: 
