No. 2.] VENTRAL ABDOMINAL WALLS IN MAN. 359 
on anatomy there is considerable difference of opinion regarding 
the positions of the transverse lines in the rectus abdominis 
muscle. No doubt this lack of agreement is due to the varia- 
tions in the arrangement of the muscle segments, for we know 
that in some instances all of them, as indicated by their inner- 
vation, may be present, while on the other hand a number of 
them may be but slightly marked or even wholly missing. As 
a rule a number of well-marked cross striations are present, but 
their position and number is differently pictured by different 
authors. Two of the newer atlases express very well the two 
views which are usually entertained. In Toldt’s! atlas a 
muscle segment is immediately opposite the umbilicus, while 
in Spalteholz’s? atlas this muscle segment is wholly above the 
umbilicus, placing the lowest transverse line immediately oppo- 
site the umbilicus. With the exception of the insertion of the 
muscle, the illustration given by Spalteholz corresponds with 
that given by Quain, Henle, Testut, as well as by our more 
popular English text-books, Morris and Gray. In them the 
insertion, as pictured correctly by Spalteholz, is given only in 
a diagrammatic way. I have examined a great number of 
cadavers with special reference to this muscle and find that the 
great majority of specimens correspond in every detail with 
Spalteholz’s illustration. 
The muscle segment immediately above the umbilicus then 
is the rule, but whether it arises from the same myotome in all 
instances is not proved until it is shown that it is always inner- 
vated by the same nerve. This question I have investigated 
carefully in a number of cadavers and find that in nearly all 
instances the muscle segment immediately above the umbilicus 
is innervated by the ninth intercostal nerve. All atlases in 
which the exact innervation of the rectus is given confirm the 
above observation.? The skin immediately over this segment 
is also supplied by the ninth intercostal nerve. This then gives 
us a very fixed point to work from in the further study of the 
1 Toldt, Anat. Atlas, Wien u. Leipzig, 1896. 
2 Spalteholz, Hand-Atlas d. Anat. d. Muscle, Leipzig, 1896. 
3 See in the magnificent Atlas of Hirschfeld and Léveillé, Pl. LIII. This figure 
is copied extensively; for instance, Quain, vol. iii, p. 309. 
P y 
4 Head, Brain, 1893, 1894. 
