DUCTLESS GLANDS IN THE CHICK. 
303 
tracing this granular mass upwards along the sides of the aorta, it was completely 
lost in the general formative mass which surrounds all these parts, and after many 
attempts I was unable to discover any connection between this body and the thyroid 
and the thymus above (as stated by Mr. Goodsir), by means of the blastemal tract 
along the aorta ; nor do I believe that any connection exists between them. The 
minute structure of the supra-renal gland at this period bears a very close resem- 
blance to the spleen on the fifth day of incubation ; it consists of nuclei about the 
size of the blood-discs, the majority of which are circular, pale, and contain in their 
interior, one, two, or even sometimes more dark granules, — nucleated spherical 
vesicles, their outer margin very delicate, the interior of the vesicle containing a 
few delicate granules. The only difference that exists between the minute structure 
of the spleen and the supra-renal gland, is the presence in the latter of numerous 
small dark granules, like fat granules, and which are in some cases accumulated in 
small circular masses. With this exception no difference can be observed in their 
minute structure at an early period. On the eighth day the supra-renal glands 
consist of two grayish white masses, \^hich lie one on each side of the aorta, 
between this tube and the upper and inner extremity of the Wolffian bodies, and 
are perfectly separate. They are elongated and rounded at both ends, but they 
do not present any external circumscribed margin. They are situated, for part 
of their extent, higher than the upper extremity of the Wolffian bodies, the upper 
margins of which are distinct and well-defined, as contrasted with the uneven 
outline of the supra-renal gland. On the right side, the gland is placed com- 
pletely above the corresponding ovary, but on the left a small part is hidden 
beneath the left ovary. The texture of the organ is opake, and darkly granular 
throughout. At this period a considerable advance is observed in the development 
of the tissues of the gland, for they even now present an incomplete vesicular 
arrangement ; this however is not surprising, when it is considered that its chief 
function is probably performed during foetal life. Its tissues have consequently a 
more rapid development than those of the spleen, an organ the function of which is 
exercised mainly in adult life. The imperfect vesicles of which this organ is partly 
formed, consists of a mass of nuclei, similar to those above described, amongst which 
are scattered a small quantity of fine dark granules; these masses of nuclei are 
arranged together in a circular form, without any investing membrane surrounding 
them ; in some cases, however, a fine membrane could be observed in one part only 
of the circumference of the forming vesicle, whilst the remaining portion was entirely 
free. Some of the vesicles were formed of a mass of smaller vesicles, in which nuclei 
were observed. The chief majority however were composed of nuclei, fine dark 
granules, and small dark circular granular masses. On the ninth day the supra- 
renal glands are yellowish white, and occupy the same situation as on the previous 
day, but even at this period are not bounded by any external circumscribed margin ; 
they are plainly separated from one another by the aorta, and although placed in 
MDCCCLII. 2 R 
