The Presidenfs Address. 
67 
of the details from the views promulgated by the gentlemen 
named. 
It appears that, in corroboration of the idea suggested by 
Dr. Harley, the openings described are in truth the 
sought-for organs of respiration — the blood-vessels when in- 
jected are seen to be congregated in the immediate vicinity 
of these cavities ; that Dr. Davy has pointed out that the 
pulmonary arteries of some of the Batrachia divide into two 
branches, one of which goes to the cutis, and is extensively 
ramified among the follicles, whilst the veins rising in this 
position are said to convey arterial instead of venous blood. 
Now the authority for this latter statement does not seem to 
be very definite, but it appears to me as of sufficient impor- 
tance to engage the special investigation of microscopists, 
either to verify or disprove the allegation j and if solved in 
the affirmative, would go very far to establish the theory 
propounded. 
In connection with the sacs. Dr. Harley describes a layer 
of parallel bands, and proceeds to remark upon the structure 
as compared with that of smooth muscular fibre, and fur- 
ther notices the occurrence of a number of oval bodies dis- 
tributed amongst the pigment-cells of the rete mucosum, not 
unlike very small Pacinian corpuscles. 
Next in succession we have two closely connected papers, 
viz., the Description of an early Human Embryo,^^ by my 
predecessor in this chair, Dr. Arthur Farre ; and one " On an 
early Human Ovum,^^ by Mr. George Blenkins, one of our 
joint secretaries. 
In each of these cases, the precise age of the aborted spe- 
cimens was not capable of accurate determination, but the 
respective authors of the papers estimate, from careful com- 
parison with specimens of known age, that the first-named 
was voided about the early part of the fourth week of utero- 
gestation, while the latter was probably a few days younger. 
Dr. Farre regrets that, in order to avoid injuring the cephalic 
portion of the embryo, when opening the sac, he cut through 
the pedicle of attachment, and was thus unable to give any 
satisfactory account of the allantois ; while in the specimen 
operated upon by Mr. Blenkins, this part was in excellent 
preservation ; and generally, the observations made by each 
one of these gentlemen form an admirable commentary 
upon those of the other. 
Dr. Farre^s remarks apply more particularly to the con- 
tents of the sac, while those of Mr. Blenkins are directed more 
with regard to the investing membranes. It is noticed by 
the former, that those organs which bring the body into re- 
