298 
MR. H. GRAY ON THE DEVELOPxVIENT OF THE 
surround it. On the eighth day the organ has increased somewhat in size, being 
now about as large as a small millet-seed, forming a round reddish projecting mass 
from the surface of the membranous fold in which it was developed, and which is 
now becoming more delicate and indistinct, as if in process of absorption, although 
its attachments still remain the same. From this period the spleen enlarges gradu- 
ally, being on the twelfth day about the size of a small pea; its colour becomes of a 
more vivid red, and its form somewhat circular ; it is held in its position by the 
vessels which proceed to it, and by a fold of membrane, the edge of which is cord- 
like, that passes from its lower end to the inferior border of the stomach, the remain- 
ing portion of the membrane in which it was developed having become completely 
absorbed. With the exception of a continued increase in the growth of the organ, 
which takes place more rapidly after the vessels supplying it are formed, its form, 
position and attachments remain precisely the same as in the adult bird. 
From the preceding observations it is seen that the spleen is developed from the 
surface of a fold of the “ intestinal lamina,” in the form of a small oval-shaped mass 
of blastema, quite independent either of the pancreas or stomach ; that in process of 
time this organ approximates more closely, although not more intimately to both 
these organs ; and as its vessels are formed, the membrane in which it was developed 
becomes absorbed, with the exception of a delicate fold, which in the adult bird 
serves to connect this organ with the stomach. 
I shall in the next place proceed to consider the development of the different 
tissues of the spleen, the observations concerning which, I think, are very important, 
as they tend to prove, not only'the glandular nature of the organ itself, but the great 
correspondence that the development of its tissues presents, as compared with the 
supra- renal and thyroid glands. 
On the Development of the Tissues oj the Spleen. 
Of the Capsule . — The first indication of the external capsule of the spleen I ob- 
served on the ninth day, in the form of a thin and delicate transparent membrane, 
which completely surrounded the organ ; its texture consisted of a fine granular 
membrane, in which were observed numerous minute nucleated fibres. About the 
twelfth day this membrane was more distinct, and more easily separable from the 
surface of the organ ; its texture was soft, of a greyish colour, consisting of a finely 
delicate granular membrane, in which numerous small nuclei, with elongated fibres 
proceeding from either end, were observed. On the eleventh day the capsule was 
more distinct, less transparent, thicker in texture, and more adherent to the parts 
beneath ; its texture being composed of numerous nuclei, contained in a granular 
membrane, with delicate fibres, some of which possessed a nucleus, but in others it 
had completely disappeared. On the twenty-first day, the capsule, although more 
distinct, was intimately connected with the parts beneath, and was composed of a 
dense mesh of delicate fibrillee, in most of which no nuclei could be detected. 
