'THE anal region in man (circumanal skin and anal canal) is extremely sensitive, yet a search of the literature reveals that little work, histological or experimental, has been done on its sensory innervation. The histological investigations of Ottaviani (1940) were mainly on small animals and mostly concerned with the rectum. However, he did note that there were nerve-plexuses made up of thick and thin fibres beneath the columnar epithelium of the rectal columns. No mention was made of organized sensory nerve-endings. In work on human adult and embryonic material Seto (I940), using his own modification of the Bielschowsky-Gros method, described intra-epithelial free endings in the anal canal and illustrated them by means of diagrams. His study was concerned particularly with the nerves crf the epithelium and no organized endings were described. Using a Cajal silver technique Sotelo (1954) demonstrated nerve-fibres at the anal canal ducts in human fetuses, although no organized endings were described. The nerve-fibres apparently supplied both endings in the skin and other endings in the glandular epithelial surface. Using Seto's method, Izumi (1955), one of his pupils, described organized endings in the anal region of man and illustrated them by drawings. He noted large and small end-formations which he believed to be two types of genital bodies. He also described and illustrated branching nerve-fibres which were thought to be simple or complex terminations according to the number of subdivisions involved in the termination. In addition, in the subcutaneous fat he found Pacinian corpuscles which he thought were rather smaller than those usually found elsewhere. He emphasized that the nerves and endings diminished markedly in number in the zona columnaris. In a study on human sigmoid colon and rectum Wang Wei Fan (1955) found myelinated fibres and branching non-myelinated fibres to which he attributed a sensory function. No end-formations were shown in connexion with these fibres. However, he noted some tangled glomerular endings lying close to the basal membrane of the epidermis at the mucocutaneous junction. These he considered to resemble genital corpuscles. Two types of ending have been described by Kantner (1957) in connexion with a deep and superficial network of fibres in the 38 submucosa at the mucocutaneous junction. He remarked on the presence of occasional Pacinian corpuscles near the anal sphincters. The rectum he found to lack organized endings and networks and to have submucosal nerve-fibres the branches of which were in close relationship to blood-vessels near the epithelium.The present study was undertaken to investigate the sensory nerve-endings in the perianal skin, the anal canal, and the adjoining rectal mucosa. A preliminary report of the findings has already been published (Duthie and Gairns, 1958). M T E R I A L AND METHODSHistological.-Material for the investigation was obtained from ten human beings whose ages ranged from 34 to 70 years. Three of the specimens were from early autopsies...

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1. The sensory nerve endings of the adult human hard and soft palates and of the uvula have been described. They consist of free nerve endings within the epithelium, of numerous organized endings mainly in the dermal papillæ, and of a few organized endings in the subpapillary region of the dermis. 2. The organized endings of the hard and soft palates show a general similarity in morphological character, but are more numerous in the former, where they also show “ultra‐terminal” fibrils penetrating the epithelium. Those in the uvula are of one type, show no “ultraterminal” fibrils and exhibit fine beading in their component fibrils. 3. Most of the organized endings are of unnamed form. Typical Meissner corpuscles are infrequent, while Krause end‐bulbs are relatively uncommon. Accessory fibres are found associated with all these types. No Pacinian corpuscles or endings of Ruffini or Golgi‐Mazzoni types have been seen. 4. An autonomic ground plexus is present in the dermis of palate and uvula. 5. No taste buds have been found.

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