Even if they were only useless, the wisdom teeth would furnish an instance of disharmony in the human body. But these teeth often are a source of trouble which, although it is not often serious, may lead to grave diseases and even to death. No other teeth are so subject to accident. This is due partly to the slowness with which they develop and to the difficulty they encounter in cutting the mucous membrane. Dental caries, moreover, is specially frequent in them.[71] The membrane surrounding them is specially subject to small lesions by which the infection spreads to adjacent parts. Inflammatory conditions frequently arise from these teeth, and tumours, caries of the jaw-bone and even diffused suppuration, leading to death, may be sequelæ of wounds of the wisdom teeth. Galippe[72] has described a case in which one of these teeth, failing to cut the gum in the normal position, made its way through the cheek. This produced an inflammatory suppuration of the cheek with numerous fistulæ and an inflammation of the masseter muscle which made it impossible for the mouth to open. Notwithstanding the extraction of the wisdom tooth that had been the cause of all these troubles, the patient died of meningitis, which had started from the tooth. Other cases have been described in which a difficult eruption of the tooth led to formation of an abscess in the bone, from which there arose a fatal abscess of the brain. Wisdom teeth may be the starting-point even of cancerous tumours. Magitot[73] writes that very many neoplasms of the jaw may be traced to a source of origin in the socket of the wisdom tooth. There is no useful function of these teeth to set against their disadvantages. It was our remote ancestors, masticating hard food, that had the advantages of these additional teeth. In man they are rudimentary organs, and provide another proof of our simian origin. The cæcal or vermiform appendage is another rudimentary organ in the human body, and is interesting from many points of view. I have already referred to its importance as definite evidence of our origin from lower animals, and shown how striking is the resemblance of the human organ to that of the anthropoid apes. It consists of a thick wall, containing glands, a muscular layer and lymphoid clumps. That it performs no function useful to man is made clear by the existence of undisturbed health in persons from whom it has been removed. Thanks to the advances of modern surgery, this organ has been removed very often, and sometimes even in cases where it did not appear to have been diseased. In a great majority of the cases, the removal of the organ succeeded well, and the patients experienced no harm, but appeared to carry on all the processes of digestion with equal completeness.