^{page 176 note *} The four cases described in the text of the occurrence of a supra-condyloid foramen in the human upper arm are not the only specimens which have come under my notice in the dissecting-room. In former years I had observed five specimens, in three of which both brachial artery and median nerve passed through the foramen, in the remaining two I had unfortunately not preserved a note of the arrangement. But by far the most complete account of the anatomy of the supra-condyloid foramen which has yet appeared has been drawn up by Professor Wenzel Gruber in an elaborate memoir presented to the Imperial Academy of St Petersburg. Vol. viii. 1859. This anatomist has collected from the works of previous writers, as well as from material which has come under his own observation, sixty-two cases in which this foramen was noticed in the human body, and in which there was at the same time a greater or less amount of variation in the arrangement of the pronator teres, the median nerve, the brachial artery or some of its branches. One of the chief features of interest connected with the supra-condyloid foramen is the circumstance that it furnishes, as an occasional occurrence in human structure, an approximation to an arrangement which is very frequently met with in some of the Mammalia. For there has now been recorded a considerable number of instances in which a distinct canal, generally with bony walls, existed in this locality in various Quadrumana, in Galeopithecus, in the Edentata and Monotremata, in many Carnivora, Marsupialia, Rodentia, and in some of the Pinnepedia; whilst it would appear to be absent in the Ruminantia, Solidungula, Multungula, and Cetacea. But though the canal would seem to occur almost constantly in all the genera of some orders and families of the Mammalia, yet it by no means follows that in other orders and families, though it may occur in one genus, that it exists in all, or even though it may occur in one species of a genus, that all the species of the same genus should possess it. Thus, as Professor Owen has shown (Article Marsupialia in “Cyclopædia of Anatomy and Physiology”), whilst it exists generally amongst the Marsupialia, yet it is absent in Dasyurus and Thylacinus; and though most of the species of Phalangista possess it, yet it does not exist in Phalangista Cookii; and whilst Gruber saw it in Erinaceus auritus, he did not find it, and I have not seen it, in Erinaceus europæus. In the Pinnepedia also it has been described by various anatomists as present in the Phoca vitulina, and Gruber has seen it in other species of the same genus. In a common seal which I dissected, I found that it only transmitted the median nerve, neither the brachial artery, nor any of its branches passed through it; in the Walrus (Trichechus), however, anatomists agree in stating that it does not occur, a fact which I have observed in three skeletons of that animal which have come under my observation. Again, in some of the Mammalia variations in its occurrence take place in individuals of the same species, a circumstance which has been noticed not unfrequently amongst the Quadrumana, though it has not as yet been seen, I believe, in the humeri of any of the Anthropoid Apes. Thus, whilst Tiedemann describes it as present in Cercopithecus sabæus and Cercocebus fuliginosus, Meckel and Otto state that it is wanting in those species; a discrepancy of statement which may probably be explained by regarding the arrangement as a variety present in one individual but absent in another. Of the skeletons of the Quadrumana personally examined, I have found the foramen absent in two specimens of the Orang, in a Chimpanzee, in two specimens of the Gibbon, in Cercocebus fuliginosus (agreeing thus with Meckel and Otto), in Macacus cynomolgus, in Cynocephalus maimon, Hapale jacchus, and Ateles paniscus; whilst I have found it present in a species of Cebus, and in the prosimian Stenops tardigradus.

^{page 178 note *} Multiplication of the bundles of this muscle lias been recognised by Arnold, Henle (Muskellchre, p. 196, 1858), and Theile (Traité de Myologie), 1843, p. 246. Theile also states that it sometimes receives a special head of origin from the inner condyle of the humerus; and Theile, Hallett (Ed. Med. and Surg. Journ. vol. lxxii. p. 12), and Henle state that it sometimes receives fibres from the radius.

^{page 179 note *} Various anatomists have recognised the occasional connection of these tendons, without however, specialising its different forms. See Theile, p. 246; M'Whinnie, Lond. Med. Gaz., vol xxxvii. p. 191; Henle, p. 196; Wood, Proc. Roy. Soc. of London, p. 301, 1864. I am disposed to regard the connection in one or other of its forms as more common than is usually supposed.

^{page 179 note †} Flg. l, t, flexor longue pollicis; p, flexor profundus digitorum. It shows the connection of the index tendon of the latter muscle with a strong musculo-tendinous band from the former, also the close union for some distance of the middle and ring-finger tendons of the deep flexor. This and the other illustrative figures, have been drawn from the dried preparations of my dissections by my pupil, Mr Richard Caton.

^{page 180 note *} Fig. 2, t, flexor longus pollicis; p, flexor profundus digitorum; s, flexor sublimis digitorum. The connection of the first and second muscles by a tendinous band passing from the index tendon of the latter to the long flexor of the thumb, is shown; also a tendon connecting the ulnar side of the superficial with the tendon of the deep flexor for the little finger; also a close connection low down the limb between the ring and little finger tendons of both the superficial and deep flexor muscles.

^{page 180 note †} The presence of slips proceeding between the flexor sublimis and F. profundus, though without precise statement as to their connections, has been recognised by Cowper (Myotomia reformata), Theile. and Wood.

I may in this place also refer to an arrangement which I saw on one occasion in the left forearm. A slender fasciculus of muscular fibres proceeded from the flexor sublimis immediately to the inner side of the palmaris longus. It ended on a tendon which passed beneath the palmaris, and joined the tendon of the supinator radii longus at the lower end of the forearm.

^{page 182 note *} The flexor communis in this case trifurcated for the third, fourth, and fifth toes.

^{page 182 note †} Fig. 3. In this and the succeeding figures, a, is the flexor hallucis longus tendon; b, the flexor communis digitorum tendon; c, the flexor accessorius. In figure 3 the flexor communis forms no portion of the deep tendon for the second toe, and after giving a slip to the flexor hallucis tendon, trifurcates for the three outer toes.

^{page 183 note *} That the tendon of the long flexor of the great toe gives off a band more or less strong to the common flexor of the toes in the sole of the foot has been almost universally recognised by anatomists, but the exact nature of the connection between them has not at all times been clearly expressed. Amongst the older anatomists, Vesalius describes this band as passing from the tendon of the great toe to the tendon proceeding to the second toe, and sometimes in an equal degree to the tendon of the common flexor for the middle toe. Diemerbroeck again states that sometimes the long flexor of the great toe is divided in the sole into two parts, one of which goes to the great, the other to the second toe, and then the common flexor sends but three tendons to the other toes. Cowper and Bidloo simply describe a connecting band passing from the proper to the common flexor, without specialising its mode of termination, and this method of description has been followed by most systematic writers in the latter part of the last century, and in the present, as Innes, Monro, Sabatier, Bichat, Boyer, John Bell. Fyfe, Cloquet, Cruveilhier, Dodd, Quain, Harrison, Hyrtl, Ledwich, Ellis, Knox, Holden, Heath, and Gray. Meckel employs, in his description of the long flexor of the great toe almost the same method as Diemerbroeck, but, in addition, states that the long flexor tendon for the second toe is for the most part formed by the connecting band and the flexor accessorius. Theile follows very closely the latter statement of Meckel, but, under the head of anomalies, he describes the connecting band as dividing for the second and third toes. Arnold gives the connecting band as strengthening the tendon for the second toe, though it often goes also to the third toe. Henle states that the strong process from the proper to the common tendon is for the most part, and at times altogether, continued into the tendon destined for the second toe. Mr Church, in a recent monograph on the myology of the Orang (Natural History Review, 1862), has also directed attention to the connection of the band from the flexor hallucis with the second and third toes. Professor Rolleston has advanced evidence to the same effect. Last of all, Mr Huxley (Reader, 13th February 1864) states, as the results of his dissections, that the tendon of the flexor hallucis longus, besides giving off the tendon to the great toe, furnishes distinct slips to the two or three succeeding digits, uniting with the tendons of the flexor digitorum and flexor accessorius. That considerable variability occurs in the mode of termination of the connecting band might almost be inferred from the different descriptions given of it by the numerous anatomists just quoted, each apparently, of those at least who go into details, basing his description on the specimen or specimens he may more particularly have examined. A more exact conception, however, of the extent of this variability may be gathered from the analysis of the fifty specimens recorded in the text.

^{page 184 note *} * It would almost appear as if some of the systematic writers of the last century had recognised the band proceeding from the flexor communis to the flexor hallucis, but not the one passing in the opposite direction. Vide Albinus, Winslow, Tarin, Sandifort, and Douglas. Several of the more recent writers have described an arrangement similar to the one recorded in the text.—Vide Sabatier, Arnold, and Theile.

^{page 184 note †} Fig. 8 shows the deep flexor tendon for the little toe entirely formed of the flexor accessorius. The flexor communis, after sending off a connecting band to the flexor hallucis, trifurcates for the second, third, and fourth toes, to which the connecting band from the flexor hallucis also proceeds.

^{page 184 note ‡} The two specimens described in the text were found amongst the fifty specimens specially analysed, but I have in former years, and in other subjects, met with additional instances of an accessory muscle in this locality. The region of the inner ankle appears, indeed, to be frequently the seat of such accessory muscular structures, e.g.

1st, A large slip springing from the inner side of the soleus, and passing quite distinct from the tendo Achillis, to be inserted into the inner concave surface of the os calcis.

2d, A muscle arising from the deep fascia of the back of the leg, and inserted into the inner side of the os calcis, close to the inner head of the flexor accessorius; this apparently constitutes the accessorius ad calcaneum of Gantzer.

3d, Two muscular bundles connected to the deep fascia of the back of the leg, one as high as the middle of the tibia, the other close to the origin of the flexor hallucis longus from the fibula; these bundles united to form a muscle which passed beneath the internal annular ligament to the sole where its tendon bifurcated, one slip joining the tendon of the flexor hallucis longus, the other the tendon of the flexor communis digitorum. A corresponding arrangement was found in both limbs.

4th, A well-marked muscle arose from the deep surface of the soleus tendon. It concealed the tendons of the deep muscles, and the posterior tibial vessels and nerves in the lower third of the leg, and was inserted into the deeper surface of the tendo Achillis, immediately above the os calcis. A similar case to this has been described by R. Quain.

Other irregularities in this locality have been recorded by Mayer, Rosenmüller, Gantzer, Meckel, Hallett, Theile, Henle, and John Wood.

^{page 185 note *} Fig. 9. d, the accessory muscle to the flexor accessorius. It has been bent out of its proper direction so as to occupy less space in the wood block, e, the displaced fasciculus of the flexor brevis for the little toe. which simply blends, without bifurcating with the deep flexor tendon for that toe.

^{page 186 note *} Fig. 10. In this drawing, f is the flexor brevis digitorum, which divides into fasciculi for the second, third, and fourth toes, the fasciculus for the fifth toe, e arises from the tendon of the flexor communis. In this figure the deep flexor tendon for the little toe is formed almost entirely from the flexor accessorius, the flexor communis contributing but a few fibres. The connecting slip from the flexor hallucis trifurcates for the second, third, and fourth toes, and the flexor communis gives off a connecting band to the flexor hallucis. Brugnone, Meckel, Theile, Hyrtl, Henle, Church, and Huxley, have all recognised the occasional origin of the short flexor tendon for the little toe from the flexor communis. In another subject I saw the fasciculus forming the short flexor tendon for the little toe arise in part from the external inter-muscular septum, and in part through fibres continuous with the muscular part of the flexor accessorius.

^{page 186 note †} Fig. 11, g, the tendon of the flexor brevis for the third toe, its junction with a slip from the expanded part of the flexor communis is represented. In both feet of a subject not included in the above analysis, I saw an arrangement similar to that represented in fig. 11, except that the slip from the common flexor tendon bifurcated before joining the two branches of bifurcation of the flexor brevis.