No. 2.] VENTRAL ABDOMINAL WALLS IN MAN. 357 
Fig. 2 is a profile of this embryo! drawn from the specimen 
before it was cut, with the outlines of the myotomes of the body 
added from a reconstruction. It shows the relation of the cord 
to the rest of the body and the extent of the myotomes have 
grown towards it. In the body itself the myotomes have 
distinct buds which are growing into the membrana reuniens, 
and each of these is intimately associated with its nerve. 
Where buds from the myotomes enter the extremities, their 
ventral tips appear to be fully blended to correspond with the 
blending of the nerves which enter the limbs. 
The extent of the growth of the myotome into the membrana 
reuniens is shown in Fig. 3. It shows the marked bud from 
the myotome. Earlier stages need not be given, and a later 
stage has already been described and pictured by Kollmann. 
There is, however, a time when the buds from certain of the 
dorsal myotomes blend to form the rectus, and I have not been 
able to obtain a good specimen to demonstrate this. A stage 
somewhat older than one pictured by Kollmann ? will no doubt 
give the rectus arising from the myotomes. <A good specimen 
of this desired stage is not at my disposal.? 
Fig. 4 1s from a reconstruction of the body of embryo XLIII, 
to which has been added the head taken from a photograph of 
the embryo before it was cut into sections. In the drawing 
only the superficial layer of abdominal muscles is shown. The 
form and extent of the rectus, as well as its relation to the 
external oblique, is indicated. The transverse lines in the 
rectus correspond with the digitations in the oblique, and 
each of these digitations with its corresponding segment in the 
1 Mall, Journ. of Morph., vol. v, p. 459. Reference Handbook of the Medical 
Sciences, New York, Supplement, pp. 184, 391, 875. /ourn. of Morph, vol. xii, 
p: 431. His’s Archiv, Supplement Band, 1897. 
2 Kollmann, His’s Archiv, 1891, Pl. III, Fig. 1. 
3 His’s embryo Ko (Aédhandl. d. k. s. Ges. d. Wiss., Bd. xiv) and one described 
by Fraser (Zrans. Roy. Acad. Med., Ireland, vol. xi, Pl. VI, Fig. 1) represent the 
missing stage between embryos II and XLIII. Since writing the above I have 
obtained an excellent human embryo from an operation for tubal pregnancy. The 
specimen, No. CIX, was hardened immediately in graded alcohol, and measured 
It mm. Sections show that the ribs are just beginning, and between them the 
intercostal muscles are sharply outlined. Projecting from them there are spouts 
which at points appear to be blended to make the rectus abdominis. 
