The importance of continuing to record and discuss anatomical anomalies was addressed recently by Hicks & Newell (1997) in the light of technical advances and interventional methods of diagnosis and treatment. Two recent radiological reports (Bradley et al. 1996; Murphy & Nokes, 1996) highlighted the diagnostic dilemma posed by a sternalis muscle in the detection of breast cancer.

The chondroepitrochlearis is an extremely rare muscular anomaly. Bergman et al. (1988) in their book on anatomical variations refer to ‘costoepitrochlearis, chondroepitrochlearis, or chondrohumeralis’ and describe the anomaly as a muscular slip which arises from one or more ribs, crosses the axilla, and inserts into the median intermuscular septum or medial humeral epicondyle. The phylogenetic significance of the muscle has received attention (Landry, 1958; Chiba et al. 1983; Bergman, 1991), and case reports with ulnar nerve entrapment and restriction of arm movements (FitzGerald, 1935–1936; Voto & Weiner 1987; Lin, 1988; Spinner et al. 1991) have emphasised its clinical relevance.

The radial nerve penetrates the lateral intermuscular septum of the arm before dividing into deep and superficial branches. It may be encountered in both anterior and posterior approaches to the humerus. An ability to accurately predict the point at which the nerve pierces the septum would be valuable during surgery in the arm, and would facilitate planning an approach to exploring the radial nerve after fractures of the distal humeral shaft. It would, in particular, make minimally invasive surgical techniques less dangerous. We dissected 20 cadaver upper limbs to establish whether the radial nerve enters the anterior compartment of the arm at a predictable level. We found that in almost every case the radial nerve entered the anterior compartment at a point within 5 mm of the junction of the distal and middle thirds of a line joining the lateral epicondyle of the humerus to the most lateral point of the acromion process of the scapula. This has not previously been described, and we believe is a useful aide-de-memoir to predicting the level at which the radial nerve penetrates the lateral intermuscular septum.

The innervation of the rat external auditory meatus has contributions from several nerves. Fluoro-gold, a retrograde neuronal tracer, was used to determine the relative contributions from neurons in cranial and spinal ganglia, and to distinguish any difference in the sensory and motor innervation between the outer cartilaginous and inner bony portions. The following ganglia were examined: the trigeminal, geniculate, glossopharyngeal, vagal, superior cervical, and dorsal root (C2-C4) ganglia. All selected ganglia demonstrated innervation of the external ear canal, particularly the trigeminal, glossopharyngeal, facial, and vagal ganglia. The geniculate and glossopharyngeal ganglia contributed more innervation to the inner osseous portion than to the outer cartilaginous portion of the external ear canal, and the vagal ganglion contributed relatively equally.

The distribution of nerves immunoreactive to protein gene product 9n5 (PGP 9n5), tyrosine hydroxylase (TH), neuropeptide Y (NPY), substance P (SP) and calcitonin gene related peptide (CGRP) antisera was investigated in the atrioventricular valves of the Sprague-Dawley rat and the Dunkin-Hartley guinea pig using confocal and epifluoresence microscopy. No major differences were noted between the innervation of the mitral and tricuspid valves in either species. For all antisera the staining was more extensive in the guinea pig valves. Two distinct nerve plexuses separated by a ' nearly nerve free ' zone were identified in both species with each antiserum tested. This was most apparent on the anterior cusp of the mitral valve. The major nerve plexus extends from the atrioventricular ring through the basal, intermediate and distal zones of the valves towards the free edge of the valve cusp. These nerve bundles, arranged as primary, secondary and tertiary components, ramify to the free edge of the valve and extend to the attachment of the chordae. They do not contribute to the innervation of the chordae tendineae. The second, minor chordal plexus, runs from the papillary muscles through the chordae tendineae and passes parallel to the free edge of the cusp. The nerves of this minor plexus are interchordal, branching to terminate mainly in the distal zone, free edge of the valve cusp and adjacent chordae tendineae. Some interchordal nerve fibres loop from a papillary muscle up through a chorda, along the free edge and pass down an adjacent chorda into another papillary muscle. The nerve fibres of the major and minor plexuses intermingle although no evidence was found for interconnectivity between them. In the distal zone between the major plexus which extends from the base of the valve and the minor chordal plexus there is a zone completely free of nerves staining with antisera to TH and NPY. Occasional nerves which stained positive for PGP 9n5, SP and CGRP immunoreactivities crossed this ' nearly nerve free zone ' passing either from the chordal\free edge nerves to the intermediate and basal zones or vice versa. An additional small nerve plexus which displayed immunoreactivity to CGRP antiserum extended from the atrioventricular ring into the basal zone of the valve cusp. Not all chordae tendineae displayed immunoreactive nerve fibres. It is concluded that the innervation patterns of the sensory and sympathetic neurotransmitters and neuropeptides examined in the atrioventricular valves of the rat and guinea pig are ubiquitous in nature. The complexity of the terminal innervation network of the mammalian atrioventricular valves and chordae tendineae may contribute to the complex functioning of these valves in the cardiac cycle.