390 
modification of the Vertebrate type as does 
the Ornithorhynchus, is one of which it was 
obviously most interesting to ascertain the 
form of the blood-discs. I have made appli- 
cations to different professional and zoological 
correspondents in Australia on this subject, 
for the transmission of a portion of recently 
drawn blood thinly spread and dried on glass, 
or preserved in its fluid state in brine and 
other menstrua of the same density as serum, 
and for the results of observations on ‘the 
blood-discs of both the Ornithorhynchus and 
Echidna. Mr. Hobson, of Hobart Town, 
Van Diemen’s Land, an accomplished sur- 
geon and comparative anatomist, has made 
the required observations on the blood of 
the Ornithorhynchus, of which he has trans- 
mitted to me the following account :—* The 
globules of the blood of the Ornithorhyn- 
chus are discoid, and measured about the 
goth of an inch, calculating two-and-a-half 
millimetres to the line. The human blood- 
globules were placed side by side with those of 
the Ornithorhynchus, and both in shape and 
size so nearly resembled each other that it was 
impossible to say which was human and which 
was Ornithorhynchus. These examinations 
were made in the presence of Mr. Ronald 
Gunn, by means of one of Oberhauser’s mi- 
croscopes ; the powers used were 250, 400, and 
800. In order to be sure that there was no 
delusion, I placed the elliptical globules of a 
Lizard’s blood beside those of the Ornitho- 
rhynchus. The tenacity and high florid colour 
of the blood, together with the greater propor- 
tional number of globules in a given quantity” 
(in the Ornithorhynchus) “ is most interesting 
in an analogical point of view.” 
From the preceding highly valuable observa- 
tions we may infer that the Ornithorhynchus 
resembles the Mammalia in the circular form, 
the size, the proportional number, and florid 
colour of its blood-dises, which correspond in 
size with those of the only Edentate species 
yet examined, viz. the Armadillo,* and conse- 
quently with those of the Quadrumana and 
of Man. 
The blood-discs of the Echidna, according 
to the observations made by Dr. John Davy on 
a portion of blood of that animal, transmitted 
to Eng!and in brine, are likewise circular. 
Heart.—The heart of the Ornithorhynchus 
(fig. 187, a, b, c) presents a rounded oblong 
form ; it is situated in the middle of the ante- 
rior part of the chest, parallel with the axis of 
the cavity. It is inclosed ina thin subtrans- 
parent but strong pericardium. 
The right auricle (6) is larger and longer 
than the left; its appendix is free and is slightly 
bifid, as in the Marsupials. It receives the 
venous blood, also, as in that order, by three 
great veins; the left vena innominata (/') de- 
scending behind the left auricle to join the 
termination of the inferior cava (h). The coro- 
nary vein also terminates in the auricle to the 
right of the inferior cava. The right superior 
* See Medical Gazette, Nov. 18, 1840. 
MONOTREMATA. 
cava (e) is joined to the left by a transverse 
branch (g). Meckel found in the heart of 
both the Ornithorhynchi dissected by hima 
deep but closed fossa ovalis, near the upper 
extremity of the septum. This structure would 
indicate that the intra-uterine existence of the : 
oung .was of longer duration than in the 
Maservialia. < 
The right ventricle (a) is capacious, with thin 
parietes. The tricuspid valve I found to consist 
of two membranous and two fleshy portions: 
the smallest of the latter was situated nearest the 
origin of the pulmonary artery, and seemed to — 
correspond with the lesser fleshy valve obseryv- 
able in the heart of certain birds, as the Ostrich; 
it is attached to the whole of the side of the 
first or adjoining membranous portion. The 
second fleshy portion may be described as ana- 
logous to the muscular valve in the Bird’s heart, 
if the lateral margin of this were detached from 
the wall of the ventricle, and the connection of 
its two extremities was preserved, the one to” 
the angle between the fixed and moveable wall 
of the ventricle, the other to the auriculo-ven- 
tricular orifice. The two edges of the lower 
half of the second fleshy portion of the valve 
in the Ornithorhynchus are free ; but those of 
the upper half are attached to the two mem- — 
branous portions of the tricuspid valve; the 
margin of the membranous part of the valve is 
attached to the fixed wall of the ventricle by 
two small chorde tendinee; and the structure 
of the valve thus offers an interesting transi- 
tional state between that of the Mammaland 
age the Bird.* ** 
e origin of the pulmonary artery is pre 
Sided with the hase’ prae vile axe 
The left ventricle has thick parietes, 
which form the apex of the heart; the mitral 
valve is membranous; the larger flap is at- 
tached to two strong columne carner; the 
smaller flap to three smaller columne. 
The smal! left auricle (c) receives two pulmo- 
nary veins. 
In the Echidna the free appendix of the 
right auricle is slightly indented. The ter- — 
minal orifice of the superior cava is protected 
by a membranous semilunar valve, ng 
from its left side. The musculi 
inati d 
verge from a strong fasciculus, which exter 
from the appendix to the orifice of the in- — 
ferior cava; this fasciculus bounds the left — 
side of a wide fossa ovalis, which is imper- 
forate. The inferior cava is protected bya large _ 
membranous Eustachian valve; the left vena 
innominata terminates by a distinct aperture te 
the left of the preceding, and is also defende 
by a process of the Eustachian valve. 1 
inner surface of the right ventricle is more irre- 
gular than in the Ornithorhynchus; the f 
wall is attached to the fixed one by set 
columne carnez and short chorde tendinew; t ne 
tricuspid valve is membranous and consists of 
one principal portion attached to the exter 
* «© Similitudo quedam cum avium valvula: ve- 
nosa dextra et propter carnositatem et aera A. 
figuram minime pratervidenda adest.”—Meckel, 
lic, p. 3l. 
