a 
1028 THE DIGESTIVE SYSTEM. 
the fifth week, as a small outgrowth of the wall of the primitive gut (mid-gut), not yet 
differentiated into small and large intestines. At this time the outgrowth 1s of the same size 
throughout, and is practically equal to the intestines in diameter. About the eleventh week, 
whilst the large and small bowels are still of the same width, it has increased very considerably 
in length (being equal to about five times the diameter of the small intestine, and thus being 
relatively as long as in the adult); but even at this early date the basal portion, for about one- 
fifth of its length, is quite as wide as the intestine, whilst the remaining four-fifths of the out- 
erowth—the future appendix—is only about one-half or one-third the diameter of the gut. 
From this it is seen that the distal portion of the outgrowth, which subsequently becomes the 
vermiform process, begins to lag behind even at this early period of its development. 
The basal portion continues to expand with the gut; the distal part grows rapidly enough 
in length, but otherwise enlarges very slowly, so that, towards the end of foetal lite, the ceecum 
has attained a conical shape, the wider end joining the ascending colon, the narrow end tapering 
eradually and passing into the vermiform process. This form, known as the infantile type of 
erecum, 1s retained for some time after birth, or even may (in 2 or 3 per cent of cases) persist 
throughout life. 
As early as the sixth or seventh month of foetal life the wall of the terminal portion of the 
small intestine adheres to the inner side of the cecum for some distance below the ileo-ceecal 
orifice. And this connexion, which is rendered more intimate by the passage of two folds of 
peritoneum, one on the front, the other on the back, between the two parts, profoundly modifies 
the subsequent growth of the czecum, and determines very largely its adult form. For, when the 
eeecum begins to expand, the inner aspect is prevented, by its connexion with the termination 
of the ileum, from enlarging as freely as the rest of the wall; im consequence of this the outer 
part grows and expands much more rapidly, producing the lop-sided appearance already referred 
to, and soon comes to form the lowest part or fundus of the caecum, and the greater part of its 
sac; whilst the original apex, with the vermiform appendix springing from it, anchored, as it 
were, to the end of the ileum, is thrust to one side, and finally lies on the inner and posterior 
aspect of the cecum, a little way below, and usually posterior to, the end of the ileum. 
The position of the cecum varies at different periods of fatal life. About the eleventh or 
twelfth week it lies immediately beneath the liver, and to the left of the middle line ; it then 
gradually travels to the right, crossing the descending duodenum, and is found lying on the 
right side, just beneath the liver, at the fourth month. From this it descends slowly to its 
adult position, which it usually approaches towards the end of foetal life, but it may not actually 
reach it until some time after birth. An imperfect descent gives rise to the lumbar position of 
the cecum, or an excess in this direction to the pelvic position (referred to on p. 1026). 
Types of Cecum.—Three chief types of cecum may be distinguished—the fetal type, conical 
in shape and nearly symmetrical, with the lower end gradually passing into the vermiform 
appendix ; the infantile, in which the passage from the cxeeum to the vermiform process becomes 
more abrupt, the outer wall more prominent, and the whole sac more unsymmetrical ; and the lop- 
sided adult form, as described above, which is the condition found in 93 or 94 per cent of adults. 
Structure.— Nothing in the arrangement of the mucous and submucous coats calls 
for special notice. The teenize or longitudinal bands of the muscular coat all spring 
from the base of the vermiform appendix (Fig. 696); the anterior runs up on the front, 
internal to the main prominence of the cecum; the postero-external runs up behind this 
prominence ; whilst the postero-internal passes directly upwards behind the ileum (Fig. 
696). The longitudinal fibres on the upper aspect of the ileum partly join the postero- 
internal tenia ; those on the front and back join the circular fibres of the large gut. 
The serous coat has, in connexion with it, certain folds and fossee which are described 
at p. 1030. 
Vermiform Process or Appendix Ceci (Fig. 698).—The appendix is a worm- 
like tubular outgrowth which springs from the inner and back part of the cecum 
about 1 to 12 inches (2°5 to 3°75 cm.) below the ileo-cecal orifice. From this it 
generally runs in one of three chief directions, namely—(1) over the brim, into the 
pelvis; (2) upwards behind the cecum; or (5) upwards and inwards towards the 
spleen; each of which has been considered to be the normal position by one or 
more observers. In the first of these situations it is quite evident as it hangs 
over the pelvic brim; in order to expose it in the second, the cecum must be 
turned upwards; whilst, in the third position, it hes behind the end of the eum 
and its mesentery, and these must be raised up in order to display it. In 
addition to the positions just mentioned, it has been found in almost every 
possible situation in the abdomen which its length would allow it to atta. In 
every case the anterior tenia of the cecum, which is always distinct, offers the 
surest guide to the process, the base of which can be located with certainty by 
following this tenia to the back of the ceecum (Fie. 696). 
Its size is almost as variable as its position. Taking the average of numerous 
measurements, its length may be given as about 35 inches (92 min., Berry), and its 
