450 The Islands of Langerhans in the Human Embryo 
cal with that described by Laguesse in the sheep, and later by Renaut in 
the human embryo. 
In another preparation (No. 4) of about the same age, although the 
preservation is also perfect, this differentiation is not so distinct. The 
study of this preparation added little to the above description. 
Very little information was obtained from a study of preparations 5, 
6 and 7. The sections had evidently been prepared for other purposes 
than the study of such minute details as this investigation required. The 
general conformation of the acinar processes can be readily made out, and 
in places groups of cells suggesting those described above are seen; but a 
study of their finer characteristics is impossible. 
In preparation No. 8 (embryo of 90 mm.) the tubular character of 
the acini is more prominent, and the solid masses of cells representing 
the primitive islands stand out distinctly by contrast. The islands are 
much larger than in No. 3, being made up of from twenty to forty or 
more cells, and are still in close relation to the acinar processes from 
which they originate. The tendency of their protoplasm to stain in- 
tensely with eosin is more pronounced than in the earlier periods. In 
this specimen the islands exhibit the first stage of vascularization which 
is shown by the presence of two, three, or four red blood corpuscles lying 
here and there between. the cells. Occasicnally in large islands a small 
capillary vessel filled with red blood corpuscles protrudes, generally from 
the acinar side, towards the center of the island. The cells of these larger 
islands show a tendency to form the intereapillary columns or groups 
characteristic of the later stages of development. About the islands the 
reticulum is somewhat differentiated so as to form a distinct capsule com- 
posed of one or two layers of cells. Besides this more advanced stage 
of development, the early stages described in No. 3 are still met with. In 
this early period no islands were found in the head of the pancreas, which 
is of interest in view of the observation of Opie (15) that in the adult, 
the islands are most abundant in the tail and body of the organ. 
Preparation No. 9 shows greater vascularization but does not differ 
otherwise from that just described. 
Preparation No. 10 is a perfectly preserved pancreas from a foetus be- 
lieved to be of the third month; it presents many points of interest. 
Numerous primitive islands are scattered through the tail and body, while 
for the first time, a few are seen in the head. These last, how- 
ever, represent the very early stages of development. Although most 
of the islands are in intimate connection with the acinus, an arrange- 
ment is frequently seen which indicates the manner in which the 
island eventually becomes separated from the acinus. As illustrated 
