Joseph Marshall Flint 419 
place.* In working up the blood supply of the submaxillary two of the 
simpler methods have been found especially serviceable, namely, the use 
of silver nitrate and a saturated aqueous solution of Prussian blue. 
The chief value of the silver nitrate method lies in the fact that by far 
a greater proportion of the silver is precipitated in the arteries, giving by 
a single injection a natural differentiation between them and the veins. 
Moreover, the endothelial lining of the blood-vessels is beautifully dem- 
onstrated by this method. A ? to 1 per cent solution gives good results. 
The only disadvantage lies in a tendency for this solution to extravasate 
somewhat more than the Prussian blue, but there is compensation in 
the fact that silver injections are usually incomplete. These give 
clearer pictures of the blood supply in the developing organ, because 
the details are not obscured by a general filling of the entire capillary 
system. Double injections are possible and serviceable in the embryos 
where it is necessary to differentiate arteries and veins, but in the sub- 
maxillary, at least, most of the differences between the arterial and 
venous systems can be clearly shown in the silver nitrate specimens. 
(Figures 2 to 8.) For the blood supply of the adult organ Prussian 
blue and lamp black gelatin or a carmine mass followed by a suspension 
of lamp black in gelatin gives very sharp pictures. The circulation in 
the adult organ, however, differs in no marked feature from that of the 
pig at birth, except quantitatively. For a study of the relationship 
between blood-vessels and cells, sections made by the routine methods 
demonstrate clearly these points. And, in following the development of 
the cellular elements of the ducts and alveoli, Mallory’s aniline blue 
connective tissue stain is of great value. This stain seems to be pecu- 
liarly adapted to the use of the submaxillary because it brings out in 
sharp relief differences between mucous and parietal cells, and stains as 
well the duct epithelium. Moreover, it differentiates clearly between 
connective tissue fibers and cell elements. 
ANGIOLOGY. 
In man, the A. submaxillaris is derived from the A. maxillaris externa, 
which runs in a small sulcus on the surface of the glandula submaxil- 
laris or directly through its substance as it mounts up over the lower 
border of the ramus of the mandible. Occasionally the A. submentalis 
contributes submaxillary branches that enter the organ. The Vv. sub- 
maxillares sometimes empty into the V. submentalis, but usually are 
tributaries of the V. facialis communis. In man the arteries do not 
3 Flint, Welch, Festschrift, and Johns Hopkins Hospital Reports, Vol. IX. 
