(A.) Atresia Palpebrarum

The eyelids are said to coalesce naturally towards the end of the third or the commencement of the fourth month, and to separate afterwards. Accordingly this malformation would be an arrest of development.

(B.) Atresia Oris

According to Burdach, the lips coalesce in the fourth month, closing the mouth until the sixth, when they again separate. According to Bischoff, however, this malformation might have a different origin. At a very early period, namely, the visceral edges of the animal layer mutually incline towards each other inferiorly, unite, and form, through the medium of Rathke's so-called inferior bond-membrane, the visceral cavity of the embryo. Not until the visceral arches break forth above, does the upper portal to the nutritive canal open, and not until still later the mouth. The atresy might, therefore, depend upon the abiding of the bond-membrane. In either case it would be an arrest of development.

(C.) Atresia Pupillce

Until the seventh month the pupil is closed by the membrana pupillaris, the anterior section of a vascular sac in which the lens, with its capsule, is inclosed. Its persistence determines the atresy.

(D.) Atresia Nasi

According to Burdach, the nostril becomes closed during the fifth week by a saccular plug, which gradually disappears during the fifth month. Its persistence would occasion the atresy.

(E.) Atresia Auris Externae

The external meatus auditorius is developed out of the posterior upper portion of the first visceral fissure. Previously to birth it is upon the whole little developed. A slight anomaly of formation may give rise to its closure, although at no period is the latter normal.

(F.) Atresia Ani

The anus is not present at first, even where the terminal intestine has formed. A stand-still at this period, however, would involve the simultaneous closure of the urinary and sexual organs, seeing that their external orifices are all developed out of the primitive orifice of the terminal intestine, - the cloaca. Where, therefore, the anus is alone closed, the mischief must date from a later period, namely, after the separation adverted to has already taken place. Some physiologists believe it to be, at a certain epoch, the natural condition.

(G.) Atresia Vulva

Probably conditional upon the turgescent edges of the external orifice of the uro-genital canal being brought into apposition, and coalescing in the female, as they ordinarily do only in the male sex, for the formation of the scrotum. Where the anus is at the same time deficient, we have here again non-development of the cloacal outlet.

(H.) Atresia Vagina

Atresia Vagina, frequently due to a preternaturally large hymen, although occasionally to a partial deficiency thereof, causing two blind sacs to overlap and compress each other.

(I.) Atresia Uteri

Atresia Uteri, not being derivable from the mode of development of the uterus, is to be regarded as a vice of formation, or else as the result of inflammation.

(K.) Atresia Urethra

Atresia Urethra, in the male, an arrest of development, - the groove at the nether part of the penis, out of which the urethra is developed, not extending to the glans. In the fourth month the glans becomes perforated, in the natural course: if this process be checked, this part will remain imperforate.

To acquired anomalies of connection belong, firstly, actual interruptions of continuity, together with their not invariable but frequent and obvious associate, diastasis, - that is, the parting, through loosening or lesion of continuity of the binding material of two bones immovably connected together, and again the estrangement and deviation of the articular ends of two bones, - luxation. Secondly, agglutination and concrescence of two or more formations originally contiguous, or brought by accident or design into mutual association, and abiding contact with one another. Agglutination is effected through the binding property of recently exuded fibrin; - concrescence through the medium of textures newly formed out of exuded protein substances, and like unto the normal textures, for example, areolar tissue; or through the medium of such as differ in certain respects, for instance, in the degree of density of aggregation, - in the arrangement of their form-elements, - in chemical composition, - cancer, for example, - and, lastly, through the medium of vessels. This species of concrescence, in accordance with the character of the binding material, is effected by loose, filamentous adhesions, admitting of a certain degree of motion in the affected organs; or by tense and intimate conglutinations.

The adhesion of the parietes of hollow organs, and the obliteration of canals and of their mouths, represent acquired morbid atresy. This originates in various ways: for example, in concentric atrophy consequent upon deficient expansive power. Thus, in ducts, it follows the extinction of the gland; in bloodvessels, the cutting off of the blood stream; or it is the effect of abiding compression and mutual contact of the parietes; or, again, it may be the result of the deposition of organic matter out of the contents of the canal, or of textural changes in its walls, produced by inflammation, cicatrization, and the like; or, lastly, of luxuriating heterologous growths.

The coalition of the two bones in mutual contact within an articulation is specially termed articular adhesion, anchylosis.