THE DEVELOPMENT OF THE RETICULATED BASEMENT 
MEMBRANES IN THE SUBMAXILLARY GLAND. 
BY 
JOSEPH MARSHALL FLINT, M. D. 
Professor of Anatomy in the University of California, Hearst Anatomical Laboratory 
of the University of California. 
WitH 9 TEXT FIGURES. 
Mall’s* recent paper on the development of the connective tissue has 
done not a little to clarify our ideas concerning the origin of these per- 
plexing products of the mesoderm. ‘Their relation and ancestry he has 
traced back to a primitive syncytium from which they are all derived. 
To explain in his own words: “The network of fibrils which forms 
Wharton’s tissue, to employ the best known example, is composed of a 
mass of anastomosing cells, a syncytium from which the connective 
tissues arise. In very early embryos the mesenchyme is composed of 
individual cells which increase rapidly in protoplasm and then unite to 
form a dense syneytium. The protoplasm of the syncytium grows more 
rapidly than the nuclei divide, so that in a short time we have an ex- 
tensive syncytium with a relatively small number of nuclei. In its form 
the syncytium appears as large bands of protoplasm with spaces between 
them filled at times with cells and at other times with fluid. The 
second condition we have in the umbilical cord of young human em- 
bryos. About this time the protoplasm of the syncytium differentiates 
into a fibrillar part, which forms the main portion of the syncytium — 
the exoplasm—and a granular part, which surrounds the nucleus—the 
endoplasm. The fibrils of the exoplasm are very delicate and anasto- 
mose freely.” From this period and these two differentiating products 
of the syncytium, Mall traces the development of cartilage, white 
fibrous tissue, reticulum, the cornea, and elastic tissue. 
In describing the syncytium of the tadpole Malls says: “The point 
I wish to leave open is whether the mesenchyme was ever composed of 
individual cells. Was it not a syncytium throughout its development? 
At any rate, it is quite evident that the earlier syncytium if it exists 
1Am. Jour. of Anatomy, Vol. I, No. 3, 1902. 
