THE GROSS ANATOMY OF A 12-MM. PIG. 
BY 
FREDERIC T. LEWIS, A.M., M.D. 
From the Embryological Laboratory, Harvard Medical School. 
Wirn 4 PLATES. 
It has been my privilege to study, with Prof. Charles S. Minot, the 
transverse sections of a 12-mm. pig embryo forming Series 5 of the 
Harvard Collection. Numerous sections of this embryo are to appear 
in: Prof. Minot’s new “Laboratory Text-book of Embryology.” To 
show the relation of these to one another I have made four recon- 
structions which are here separately presented as the basis of this paper. 
It is thought that this particular pig is distinguished from all other 
embryos of corresponding size by the detail and completeness with 
which the entire animal has been portrayed. Similar figures of the 
human embryo are found in Pl. XX, Vol. 5 of the J ournal of Morphol- 
ogy (Mall, g1), and in Taf. II of His’s contribution “ Zur Geschichte 
des Gehirns,” 88. 
The reconstructions were made generally by the method of His. The 
contour of the brain and pharynx was taken from wax models prepared 
by Dr. J. L. Bremer; elsewhere the shading has been inferred from 
studying the cross sections. Since the umbilical cord was cut away 
in the embryo of series 5, that region was supplied from another trans- 
verse series of a 12-mm. pig, No. 518 of the Harvard Collection. 
The general description of the illustrations 1s left to the lettered 
figures. Only the more interesting features are presently to be de- 
scribed ; first, those concerning the brain, nerves, and sense organs ; then 
those involving the pharynx, digestive tract, and viscera; finally, those 
relating to the vascular system. 
Brain, Nerves, and Sense Organs.—The exterior of the brain and 
nerves appears in Plate I; the internal aspect of the brain in Plate ITI; 
and the internal view of certain nerves in Plate 1V. Unfortunately the 
depression between mid-brain and diencephalon has been exaggerated 
in some of the figures. In the median plane the superficial surface is 
not indented at this point. The rounded outer wall of the diencepha- 
Jon shows no trace of the epiphysis which begins to form in a pig of 
