304 
MR. H. GRAY ON THE DEVELOPMENT OF THE 
close contact with the Wolffian body, their different structures at once show them to 
be distinct organs ; for the dark opake granular structure of the supra-renal glands 
contrast most strongly with the lighter and more transparent tissue of the Wolffian 
bodies. The vesicles of which the organ is at this period composed are circular, or 
elongate oval, and their contents far more transparent than those observed at a later 
period of development. They now present a delicate but well-defined external invest- 
ing membrane, containing nuclei and a few dark granules. On the tenth day (fig. 10) 
the supra-renal glands are pyriform, the broad end being direeted upwards, and the 
apex downwards ; their margins are now also distinctly circumscribed, and their 
tissue, although dark and opake (when seen with a low magnifying power), is more 
transparent than the tissue of the gland at a more advanced period of its develop- 
ment. The vesicles of which they are composed at this period are not all circular, 
for some are elongated, and present two or sometimes three hemispherical bulgings 
on their wall, as if apparently formed of the junction of two or more vesicles; these 
contain several nuclei and numerous small dark highly refractive granules ; the former 
are however at this period far more numerous than the latter. These vesicles vary 
both in size and form ; they are grouped together in a mass, in which it is as yet 
impossible to detect any subdivision into cortical or medullary portions. On the 
fourteenth day (fig. 11) the supra-renal bodies have somewhat changed their position ; 
they lie at the back part and inner side of the upper extremities of the Wolffian 
bodies, and in front, and at the inner side of the upper end of the kidneys ; their form 
is of an elongated oval, and the one on the left side is like the corresponding ovary, 
slightly the larger of the two. At this period they are connected with the Wolffian 
bodies through the intervention of a delicate web of areolar tissue. The inferior 
vena cava is now observed passing upwards between these bodies, and closely adhe- 
rent to their inner sides. On examining the organ with a low magnifying power, it 
is seen to consist of a mass of vesicles, which however are not equally distributed 
throughout the whole of its substance, being aggregated in much larger quantities 
at the upper, lower, and outer sides of the gland than at its inner side, where it is 
connected with the vena cava, and at its centre. These vesicles are large, and radiate 
from the circumference towards the centre of the gland, in some cases complete 
tubes of some length being formed by their junction, as indicated by hemispherical 
bulgings along their walls. They lie between the meshes of a close plexus of vessels, 
which run in straight lines from the centre towards the circumference of the gland. | 
These vesicles, at this period, and up to the time when incubation is completed, cou- j 
sist of an external investing membrane, so delicate as to render its demonstration a i 
matter of some difficulty ; they are full, not of nuclei, as was observed during the 
first stages of development, but of dark and highly refractive granules, precisely like I 
oil-globules, in such numbers as to completely distend the cavity of the vesicle, and j 
also prevent the nuclei, a few of which still exist in small numbers, from being clearly i 
detected. By the eighteenth day (fig. 12) the glands have enlarged considerably, and i 
