[ 3i6 ] 
Here are evidently in this foetus two diftin^l fyflems of 
vefiel^, arteries and veins r</;, that carried red blood It 
is plain alfo, that the blood palled from the internal iliac 
arteries, through the bypogrq/trics and umbilicals to the 
placenta^ and was returned from it by the umbilical vein 
to the navel, and thence dilfributed in the manner be- 
fore obferved. But as there is no heart, nor any thing 
analagous to one, it becomes extremely difficult to afcer- 
tain the powers by which the circulation was carried on 
through this curious phyliological phaenomenon. May 
we not however venture to advance a conjeilure, that 
the periftaltick, or living mufcular power of the arteries, 
was principally fubfervient to this important end ? Many 
examples are to be met with in the coUecftions of the cu- 
rious and learned in the different parts of Europe 
which 
(d) Mr. HEWSON attempted to inje£l the whole blood vefTels by the umbili- 
cal vein as ufual. To his great furprize, no part of the injection returned by 
the umbilical arteries. He could not account for this fingularity at that time ; 
but as only a part of theveffels were filled, he injefted afrefli by one of xhthyps- 
gajlric arteries. Upon difiTeftion afterwards, this myftery was unravelled by the 
heart’s being totally abfent. It then appeared alfo, that by the firll Infpeftion 
he had filled the venal fyftem, and by the latter the arterial. 
(c) See a very curious cafe related by Monf. winslow, in the Memoires de 
L’Academle des Sciences for 1740, p. 586. and 604. Among other remarkable 
fingularities in this little monftrous abortion of fix months, that excellent ana- 
tomifl: particularly takes notice, that there was no appearance of one drop of red 
blood in any of its veffels, which were univerfally filled with a ferous lympth; 
and that there were no veftiges of any veins at all. 
(f) F. LiCETUs, de Monftris,p. 300. et feq. palfyn, Traite des Monftres, 
p. 325. cheselden’s Anatomy, 5th ed. p. 379. Phllofophical Tranfaflions, 
1739-40, N° 456. p- 303. Ibid. 1767, p. I. L’Academie des Sciences, Hift. 
1720, 
