454 The Islands of Langerhans in the Human Embryo 
at the sixth or seventh month, except that the latter has a larger pro- 
portion of connective tissue. In other words, at the latter period, we 
have the development of the third month plus the connective tissue pro- 
duced by the syphilitic process. This arrest of development is shown in 
Fig. 3, which is taken from a specimen of syphilitic pancreatitis in a 
foetus 21 cm. long. 
Summary.—The islands of Langerhans (embryo of 54 mm.) originate 
through a proliferation and differentiation of the cells of the primitive 
secreting tubules. The differentiated cells characterized by a rich, finely 
granular, eosinophilic protoplasm le as small round or oval masses in 
direct continuity with the cells of the tubule. Later (embryo of about 
the third month), the attached portion becomes constricted, and lengthen- 
ing, forms a stalk-like, solid process of cells connecting the island with 
the acinus. At this period, a few entirely isolated islands are present. 
A separation takes place and apparently is brought about by the pressure 
of the investing connecting tissue. Vascularization has now occurred. 
In still later stages a progressive vascularization, increase of cells, ar- 
rangement of the cells in columns, and appearance of a fine reticulum are 
observed. The rapidly forming glandular structures finally surround 
the islands which then occupy the centers of the lobules. 
In syphilitic pancreatitis of the new born, a condition in which the 
normal development of the pancreas is arrested by a rapid proliferation 
of connective tissue, confirmatory evidence of this mode of development is 
supplied by the presence of solid processes of cells connecting the islands 
and acini. 
The demonstration of the differentiation and final independence of the 
islands of Langerhans as here given offers an anatomical basis for the 
theory, so strongly supported by pathological and experimental observa- 
tions, that the islands have a physiology independent of the glandu- 
lar portion of the pancreas. 
REFERENCES. 
1. LAGuUESSE.—Jour. de l’Anat. et de la Phys., 1894, XXX, 731; 1895, XX XI, 
475; 1896, XXXII, 171, 209; Verhandl. der Deutsch. Anat. Gesellsch., 
NSO 4. 
2. DLAGuUESSE.—C. R. de la Soe. de Biol., 1889, LI, 900. 
3. DIAMARE.—Internat. Monatschr. f. Anat. u. Phys., 1899, XVI, 155, 177; 
Anat. Anzeiger, 1899, XVI, 481. Quoted by Oppel, Lehrb. d. Ver 
gleich. Mikr. Anat. d. Wirbeltiere, 1900, III, 800. 
4, MAssAri.—Rend. R. Accad. dei Lincei., 1898, VII, 134. Quoted by Oppel. 
or 
RENAUT.—Traité d’Histologie Pratique, 1899, IT, 1523, 1543. 
