of Perodicticus sends two tendons to the fourth, one to the third and one to the fifth finger. In Nycticebus it has five tendons whereof the fourth digit gets two. It is divided into two halves to above the middle of the forearm of Cheiromys; of these, the radial belly gave tendons to the index, third and fourth digits; its ulnar belly sends tendons to all the digits except pollex.

EXTENSOR DIGITORUM PROFUNDUS (extensor indicis proprius et extensor pollicis longus proprius). At first I thought extensor indicis proprius was absent from the Orang, but found what seemed to be a new muscle to which I gave the above name appropriate to its situation and function; but afterwards, from its relative position I determined it to be the homologue of extensor indicis proprius, although it is a flexor digitorum inserting on the three middle fingers of the Orang. It has a narrow origin between the proximal thirds of the ulna and radius, from the superior fascia of supinator brevis, from the posterior aspect of the ulna and from the interosseous membrane on the ulnar side. It divides into three fasiculi; the upper and largest fasiculus, which goes to the ring-finger, being distinct almost to its origin; while the other two, separate a little above the annular ligament where they become tendinous. They insert on the bases of the three middle fingers, each by a broad aponeurosis. In Pithecia hirsuta there exists a flexor digitorum communis profundus representing both extensor pollicis longus and extensor indicis proprius, acting on the thumb and first three fingers. This same communis form attains also in Hapale penicillata, but the thumb receives two tendons instead of one. The portion to the thumb is more distinct in the higher apes where it is generally single as in man. The indicial portion is like that of man in the Gorilla alone. In Hylobates leuciscus it has three tendons all acting on the medius finger, but in all the other higher apes it has two tendons acting on the index as well as medius. In the lemuroids we see again that this muscle as found in man is but a remnant of an extensor digitorum communis. It sometimes acts as an extensor of index alone in Loris gracilis and the lemurs, but their third finger usually receives also a tendon. That of Galago and Tarsius attaches rather constant to both the second and third digits. Lemur catta has it as an extensor of the three middle fingers, and its parts are only separate from the wrist onwards. These are divisible into the belly of the

muscle in Cheiromys, where it is still more complex since the indicial part is very delicate, but sends an additional factor to medius, while the middle one is the largest and gives off an extra slip to assist that to the fourth. It goes either to the second and fourth or to the second and fifth digits in Nycticebus and Perodicticus. From these complex and various insertions it is plainly seen that we can no longer speak of extensor pollicis longus proprius and extensor indicis proprius, as distinct muscles, but rather as more or less differentiated parts of an extensor digitorum communis profundus. The most important part of it often goes to the median finger as in Cheiromys and Lemur xanthomystax. In the latter this is as distinct as a separate muscle, and is the homologue of the radial extensor of the third finger sometimes found in man as extensor medii digiti.

FLEXOR DIGITORUM COMMUNIS PROFUNDUS (et flexor pollicis longus proprius). That flexor pollicis longus of man is only a differential part of flexor digitorum com. profundus, is plainly seen, although Bischoff says that it does not exist at all in the apes, while at the same time he describes it as a minor part of flexor digitorum communis profundus, failing to see its homological value. Mivart, Muric, and others, are equally mistaken in describing the major part of flexor dig. com. l. profundus as the flexor pollicis longus proprius. It is said not to exist in the Orang because the thumb receives no tendon, and it is not distinguished from the flex. dig. c. l. profundus. In the Gorilla it goes to the two first digits, that to the thumb being the weaker, while the flexor dig. c. 1. p. acts on the other three fingers. In the Chimpanzee f. d. c. l. p. has its belly divisible into three portions; of these the radial one represents the so-called flex. poll. proprius longus and sends one of its tendons to the thumb. It maintains the same insertions in Hylobates leuciscus, but is not in the least separable from the fl. dig. com. I. profundus, which exists here with one large entire belly in its typical form flexing all the digits. The same is again seen in Hapale penicillata. In all the other apes it exists as one large flexor communis, usually having a single tendon at the wrist which sends the deep flexor tendons to all the fingers and the thumb also, except in Perodicticus where the index receives none. The proximal part of the belly however, is often more or less divided; two main parts, one radial and the other ulnar are most common.

Of these the pollical half is generally the largest in the lemuroids. Minor partial divisions often exist also, so that there are four parts of the original belly in the galagos and Macacus cynomolgus.

OPPONENS MINIMI DIGITI seems to be absent from the Orang, but the other muscles of the little finger do not differ particularly from those of man. The opponens is distinct in the lemuroids.

EXTENSOR OSSIS METACARPI POLLICIS of the Orang, is smaller than the EXTENSOR POLLICIS PROPRIUS, but is quite large in the Chimpanzee. The other muscles of the thumb not already mentioned in the Orang are like the same in man. FLEXOR BREVIS POLLICIS is generally not altogether distinct from the ABDUCTOR POLLICIS in the lemuroids, where this latter muscle arises from the annular ligament and a sesamoid bone in front of the trapezius. Abd. pollicis has a double insertion in Hylobates, Cercopithecus and Macacus, while a tendency to division is noticed in some other species. The Lemuroidea have a large ADDUCTOR POLLICIS arising from the whole length of the third metacarpal and the base of the second and the palmar fascia. In Tarsius and Lemur xanthomystax, it is more or less divisible into two parts, while a distal fasiculus of it represents a TRANSVERSUS MANUS, of which the adductor pollicis would seem to be a differentiated part. This homotype of transversus pedis is strikingly distinct in the Aye-aye. This adductor (transversus) is likewise united with AD. OBLIQUUS in the higher apes, except in the Chimpanzee, Cynocephalus, Pithecia hirsuta and Hapale penicillata. The lumbricales manus do not differ from those of man. Only three exist in Galago Allenii, Cheiromys and Perodicticus, but the other lemuroids have four.

INTEROSSEI MANUS. The dorsals were very small while those of the palm were largely developed in the Orang. In the Lemuroidea each digit except pollex has a pair of interossei (flexores breves), ABDUCTOR MINIMI DIGITI being one. These are more or less divisible into internal and external (palmar and dorsal) layers. FLEXOR DIGITI MINIMI is not distinct from the abductor except in Lemur varius and L. xanthomystax. In Galago, Cheiromys and Tarsius, two superficial interosseal slips exist. Deep in the vola manus as well as in the planta pedis, Bischoff finds small MUSCULI CONTRAHENTES in all the higher apes except the Orang and Gorilla.

REFERENCES.

1. Bischoff. Beitraege zur Anat. des Hylobates leuciscus u. zu einer vergl. Anat. der Mueskeln der Affen u. des Menschen, Muenchen, 1870.

2.

Burmeister. Beitræge zur Kenntniss der Gattung Tarsius, Berlin, 1866.

3. Coues. Antero-posterior symmetry with special reference to the muscles of the limbs. The Medical Record, New York, 1870.

4. Duvernoy. Des charactères anatomiques des grands singes pseudo-anthropomorphes. Archives du Museum, VIII, 1855.

5. Gegenbaur. Vergleichende Anatomie, Leipzig, 1870.

6. Huxley. On the Position of Man in Nature.

7. Koelliker. Entwickelungsgeschichte des Menschen u. d. hoeheren Thiere, Leipzig, 1861.

8. Meckel. Anat. Comp. Traduit par MM. Riester et Alph. Sanson, 1830.

9. Mivart and Murie. On the Anat. of the Lemuroidea. Zool. Trans., Vol. VII. Part I.

11. Owen. Anat. of the Orang-utan (Simia satyrus). Proc. of the Committee of Science, etc. Zool. Soc. London. Part I, 1830.

a. b.

Cheiromys. Trans. Zool. Soc., Vol. V.
Comparative Anat. of Vertebrates.

12. Pagenstecher. Zoologischer Garten, VIII, 1867.

13. Schroeder van der Kolk & W. Vrolik. Stenops. Bijdragen tot de Dierkunde, uitgegeven door het Koninklijke Zoologisch Genootshap Natura Artis Magistra, Erste Deel. Amsterdam, 1848-54.

14. Traill. Observations on the Anat. of the Chimpanzee. Wernerian Transactions, Vol. III, 1818.

15.

(This was not a Chimpanzee, but an Orang.-W. S. B).

Van Campen. Verhandelingen der Koninklijke Akademie van Wetenshappen. Amsterdam, 1859.

a.

16. Wilder. On Morphology and Teleology. Mem. Bost. Soc. Nat. Hist., Vol. I. Intermembral Homologies. Proc. Bost. Soc. Nat. Hist., 1871. Contributions to the Comp. Anat. of the Chimpanzee. 17. Wyman. Symmetry and Homology in limbs. Proc. Bost. Soc. Nat. Hist., 1867.

b.

EXPLANATION OF FIGURES.

FIG. 1. A, ENTOGLUTEUS.

B, PYRIFORMIS.

C, MESOGLUTÆUS.

D, D, OBTURATORES.

E, E, QUADRATUS FEMORIS.

FIG. 2. A, CIRCUMDUCTOR SUPERIOR.
B, CIRCUMDUCTOR INFERIOR.

C, ADDUCTOR BREVIS.

D, ADDUCTOR LONGUS.

E-F, ADDUCTOR MAGNUS.

G-I, PECTINEUS (Origin and insertion).

K, GRACILIS.

L, ILIUM.

P, OS PUBIS.