140 PROCEEDINGS OF SOCIETIES. 
The first section of the paper is devoted to the discussion 
of the aggregation of the corpuscles of the blood. It is 
shown by the author that the rouleaur “are simply the re- 
sult of the disc-form of the corpuscles, together with a cer- 
tain, though slight degree of adhesiveness, which retains 
them pretty firmly attached together when in the position 
most favorable for its operation, namely, when flat surface is 
applied to flat surface, but otherwise allows them to slip very 
readily upon one another.” The aggregating tendency of 
the red discs is thus regarded as a phenomenon similar in 
kind, though inferior in degree, to the well-known adhesive- 
ness of the white corpuscles. It is further shown, from 
numerous experiments, that the red corpuscles vary remark- 
ably in adhesiveness, in consequence of changes in physical 
circumstances, or very slight chemical action. 
Section II is on the structure and functions of the blood- 
vessels. 
The thinness of the capillary wall is believed to favour the 
mutual interchanges between the blood and the tissues, but 
the consideration of some facts of physiology leads the author 
to the conclusion, that notwithstanding the distending force 
of the current of blood, the liquor sanguinis is not effused as 
a whole among the tissues in a state of health; and this is 
thought to imply that there subsists a mutual repulsion be- 
tween the materials of the capillary wall and the elements of 
the liquor sanguinis, preventing the passage of the latter into 
the pores of the former, except in so far as they are attracted 
by the tissues for the purposes of nutrition. 
The heart is believed by the author to be the sole cause of 
the circulation of the blood im the frog’s foot, and it is proved 
experimentally that other sources of movement cannot have 
more than a very trivial influence, and that their cessation, 
supposing them to exist at all, does not give rise to arrest of 
the blood or accumulation of corpuscles in the capillaries. 
Distinct evidences of muscularity and contractility have 
been detected in the veins of the frog’s foot, but compared 
with the arteries, the veins show very little spontaneous con- 
traction. 
Regarding the influence of changes in arterial calibre upon 
the blood in the capillaries, the author is led to conclude 
that “the arteries regulate by their contractility the amount 
of blood transmitted in a given time through the capillaries, 
but neither full dilatation, extreme constriction, nor any in- 
termediate state of the former is capable per se of inducing 
accumulation of corpuscles in the latter.” 
The influence of the nervous system upon the arteries has 
