Richard Mills Pearce | 451 
in Fig. 2, an island may be almost entirely separated from the acinus; 
the only evidence of continuity being a solid stalk-like process of cells. 
In the acinar portion of this process, a Sail seh 
Pp I SO MASE SES: 
gradual transition of the cells from the LB ees see Ss aC 
e, of — % WS a aX 
type of the gland to that of the island 
may be traced. Most of the cells in the 
process are identical almost with those 
in the island. Followed through a series 
of sections, such an island has no con- 
nection with the acinus other than this 
solid process. The connecting process 
is In some instances short and broad, in 
others long and narrow; occasionally it 
may be constricted by the surrounding 
tissue as though about to be completely 
separated. Indeed, in this series com- 
pletely separated islands are seen in the 
splenic portion for the first time. 
A careful study of this stage of the 
development has convinced me that the 
separation of the island is brought 
about by an encroachment of the ,,F!G- 2. Pancreas of an embryo of 
: : f about the third month. A fairly well 
connective tissue, causing an attenua- developed island of Langerhans is seen 
connected with the gland acinus by a 
tion of the connecting cells and their Sid process of cells. 
final disappearance between the island and acinus. The island then 
lies free to one side of the primitive acinus in a mass of connective 
tissue ; a condition just the reverse of that in the adult pancreas. Later, 
in the fifth and sixth month, when the rapid development of the acinus 
occurs, the glandular elements surround and enclose the island, and it 
then occupies the center of the lobule. The isolated appearance of the 
islands at this period of separation recalls and seems to support v. Hanse- 
mann’s view that the islands develop from the cells of the connective tis- 
sue. Without the knowledge of the earlier stages of proliferation and 
temporary connection with the acinus which I have described, their 
isolated position would indeed be inexplicable. From vy. Hansemann’s 
description, I cannot discover that he studied embryos of a period cor- 
responding to that represented by No. 3 of my series. 
The advanced vascularization at this stage affords evidence of the 
manner in which the vessels enter the island. Unlike the glomerulus of 
the kidney, to which the island is somewhat analogous owing to its very 
rich capillary network, we have not one, but several afferent as well as 
ie 
@ DP aie 
K.M Hall. fee. ; 
