Speech may be markedly disturbed, reverting to the condition of Haeckel's Homo-alalus in the shape of deaf-mutism, which is one of the extreme expressions of degeneracy. Not less than 93 per cent. of the cases of congenital deaf-mutism possess deformities of the head, face, jaws, and teeth. The mere fact of the exceedingly primitive structure of the internal auditory mechanism has abnormal or defective hearing power as a consequence. Many cases of congenital deaf-mutism owe their origin to this, inasmuch as the auditory mechanism is not in a condition to appreciate sound, even though the individual may not have been born deaf, and the whole auditory apparatus subsequently degenerates. A mental defect is sometimes superadded, thus aggravating the case. Upon general principles, since deformities of the head, face, jaws, nose, antra, vaults, &c., are common in neurotics and degenerates, stigmata of the ear-bones must occasionally take place. From the complicated structure of the ear, lesions must often result from such deformities. The deaf-mutism here considered is the result of congenital conditions not produced by disease. Dumbness may result from congenital defects of the tongue or deformities of the larynx of an atavistic or a degenerate type, but degeneracy rarely extends so deeply into the organism as in the case of deaf-mutism. No greater error is committed than the confusion of deaf mutism secondary to ear disease with the congenital type. The most prominent reversional tendencies occur in the genitals. One very common condition is retention of the testicles within the abdomen (_cryptorchidism_), which has been already pointed out, and may represent the last expiring trace of degeneracy. The testicles may, however, be perfectly normal in structure and function. In the female the uterus may present every type of mammalian uterus from the marsupial up. The female may also revert (as more rarely the male) to the condition of the reptiles and oviparous mammals in which the urinary organs and bowels empty into a single opening, the cloaca. This condition has been found in the female offspring of degenerate families, who are otherwise normal and who have produced children, despite the cloaca. Another reversion is the occurrence of breasts without nipples, resembling those found in the oviparous mammals. The breasts in degenerates, as already shown, are frequently multiple, sometimes because the law of individuation is reversed, but more often as a reversion to the many-breasted condition (_polymastia_) of the precursor of man.[236] The human kidney and liver may revert not merely in function alone to the sauropsida, but also in structure.