These anomalies (vitia nexus) consist in diminution or total absence, or else in enhancement of the natural connection and contiguity of organs. They are both primitive and acquired, and, in either case, exceedingly various in degree and extent. To the former belong the opposite extremes of cleft-formation, and of malformation from fusion, together with atresia.

1. Cleft-Formations

(a.) A considerable number of these have their foundation in the germ being originally a membranous expansion, the edges of which incline towards each other, eventually meet, and thus form into cavities or cylinders.

The two cavities developed out of the animal layer of the germ, for the inclosure of the central nervous system and of the organs of the neck, the thorax, and the abdomen, are formed out of the union of the so-termed abdominal and visceral plates. Now, supposing the union of the edges of these plates not to take place at all, or to take place but imperfectly; or supposing consummated union to become redissolved through some agency, like the accumulation of watery fluid; there would result, either anteriorly or posteriorly, and commonly at the median line, although often elsewhere, a cleft or gap, attended by prolapse, or even by destruction of the implicated viscera. Clefts of this kind are: -

Cleft skull (hemicephalia).

Cleft spine (spina bifida).

Cleft countenance.

Cleft cheek.

Cleft palate.

Cleft upper-lip.

Cleft tongue.

Cleft in the thorax.

Cleft in the abdomen.

Cleft in the pelvis.

Cleft urinary bladder, so termed prolapsus, inversio vesicae. Cleft dorsum penis (epispadiasis).

The last two are generally combined with cleft pelvis.

The intestinal canal is in like manner developed out of an expansive formation, the united vascular and vegetative layers of the germ, by the approximation of its edges, out of a groove in front of the vertebral column. Hence, clefts occur in the intestinal canal, in the stomach, as arrested growths.

(b.) Other clefts, besides those mentioned, originate in the gaps which occur during the normal development of particular parts, not closed at the proper time. To these belong:

Cleft Choroid Membrane And Iris (Coloboma Iridis)

In the embryos of all vertebrata we meet, at an early period, at the inner, lower angle of the eye, with a narrow colorless stripe in the choroid membrane, which commonly disappears before the iris becomes developed. When this stripe continues beyond this period, it often abides in the iris, and is perceptible after birth.

Cleft at the side of the neck, congenital fistula of the neck, founded in the mode of development of the visceral cavity of the head. The visceral edges of the animal layer of the germ do not grow towards each other in continuity, but in ridges, termed visceral or branchial arches, which are parted by fissures, termed visceral or branchial clefts. When the early closure of these does not take place, occasion is given to the somewhat rare malformation in question.

Cleft Urethra And Scrotum (Hypospadiasis) Of Various Grades

At an early period is discoverable, at the lower side of the rudiment of the penis, a groove, which extends to the common orifice of the urinary and sexual organs. In the male, the edges of this groove being brought into apposition, coalesce into a raphe or suture, and thus form at once the scrotum and the urethra. Where this process wholly or partially fails, there arises a malformation which, if the penis be at the same time short and the testicles retained within the abdomen, simulates female development - a form of spurious hermaphroditism.

To this malformation succeeds -

Cloacal formation, junction of the orifice of the anus and of the external orifice of the urinary and sexual organs - a formation which, being at an early period normal, may, through an arrest of development, become persistent. In the male it is necessarily associated with the last-mentioned vice of formation, that is, with hypospadiasis, frequently also with cryptorchism.

(c.) As cleft-formations may likewise be reckoned the persistence of certain communicating apertures between parts which, at a later period, ought to remain separate, as also the abiding patency of certain canals, namely:

Defective development of the septa of the heart's ventricles and auricles; permanent patency of the foramen ovale. These septa form only gradually within the heart, the septum of the auricles not arriving at its full development until after birth. Defective development of the septum of the ventricles occasions a resemblance with the hearts of fishes and of reptiles (the crocodile excepted), and especially of serpents and tortoises; e of the septum of the auricles a resemblance, in particular, with the hearts of fishes. It is often quite evident that the arrest of development has been caused by endocarditic changes in the valves - the residue of foetal valvular inflammation.

Abiding of the ductus arteriosus, ulterior dilatation thereof. Abiding patency of the ductus venosus Arantii, giving rise to the abduction of a portion of blood from the vena portse into the vena cava.

Abiding patency of the processus vaginalis peritonaei (the upper portion of the tunica vaginalis testis), so commonly the cause of congenital hernia or hydrocele. Generally speaking, the inguinal canal closes immediately after the testis has, in the seventh month, descended into the scrotal sac, carrying with it a process or continuation of the peritonaeum. Occasionally an arrest of development prevents the said closure from taking place.

Abiding patency of the urachus, allowing the escape of urine through the umbilicus. Urachus and urinary bladder are the portions of the allantois internal to the embryo, which is destined to convey the umbilical vessels from the embryo to the external membrane of the ovum (chorion), for the formation of the placenta. The portion of the allantois external to the umbilicus becomes obliterated at an early period. Of the internal remnant the inferior portion becomes developed into the urinary bladder, whilst the portion intervening between that and the umbilicus, contracts into a cord, the urachus.

Cleft member (schistomelus) commonly appears from between the third and fourth fingers or toes to the wrist or ankle. It is probably derived from external causes, and, as Gurlt infers from an examination of the foetus of a dog, from adhesion to the amnion.