Anatomical studies on the pollicis et indicis accessorius and indicis radialis muscles were conducted on 952 upper limbs from 476 Japanese adult cadavers. Each anomalous muscle occurred between the pollicis longus proprius and indicis proprius muscles in the dorsum of the forearm and hand.
The pollicis et indicis accessorius muscle was present in 13 of the limbs (1.4%). It was not coexistent with another anomalous muscle of the profundus mass in 9 cases, and it was coexistent with that muscle in 4.
The indicis radialis muscle was present in 34 limbs (3.6%). It was accompanied by another anomaly of the profundus mass in 5 cases, and not accompanied by that muscle in 29.
The pollicis et indicis accessorius and indicis radialis muscles were innervated by the posterior interosseus nerve of the radial nerve. It seems that the former anomalous muscle supplies the control of the thumb and index finger, and the latter one of the index finger only. Each anomalous muscle was considered to be differentiating on the radial side of the profundus mass in humans.

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An anatomical study on the profundus muscle was made using 832upper limbs from 416 Japanese adults. The separate muscles derived from the profundus consist of 10 kinds: namely, the pollicis longus, pollicis et indicis accessorius, indicis radialis, indicis proprius, indicis ulnaris, indicis et medii accessorius, medii proprius, annularis proprius, carpi profundus and digiti brevis. The configuration of the muscles (except for the digiti brevis) in the upper limb was classified into 13 types according to their arrangement and insertion. The most frequent type involved coexistence of the pollicis longus and the indicis proprius: it was observed in 664 limbs (79.8%). The next type involved coexistence of the pollicis longus, indicis proprius and the medii proprius: it was observed in 67 limbs (8.1%). It appears that the digiti brevis of man is derived from the most ulnar part of the profundus which does not migrate proximally.

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The antebrachium of domestic animals supports the trunk against gravity and generates propulsive force. The antigravity action of antebrachium is attributed to the contraction of flexor muscles of the carpal and digital joints. Mammalian skeletal muscles consist of myofibers, which are histochemically classified into type I, type IIA, and type IIB myofibers, of which composition reflects the proportional involvement of the muscle in varying function, such as posture maintenance and locomotion. The physiological cross-sectional area (PCSA), which are calculated from muscle volume, myofiber length, and pennation angle, reflects the maximum force of muscle. In the present study, we evaluated the PCSA of myofiber types in the antebrachial musculature and determined the magnitude of contribution from individual muscles toward varying actions of carpal and digital joints. The carpi ulnaris and flexor superficialis muscles possessed a large proportional PCSA of type I myofibers, indicating the role for these muscles in maintaining a standing posture. The additional force required for walking/running was primarily provided by the flexor profundus caput humerale and carpi radialis muscles. The proportional PCSA of myofiber types reflected the force generated for varying muscular function and provided insights into the dynamics of carpal and digital joints.

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The myofibers of the skeletal muscle vary in length in muscle and from muscle to muscle. Information about myofiber length and myofiber arrangement is necessary to understand the architecture of muscles and differences in myofiber length in muscles. The purpose of the present study was to determine myofiber lengths, ratio of myofiber length to muscle length, and myofiber arrangement of the antebrachial and leg muscles in the sheep. The myofibers of the antebrachial muscles ranged from 7.3 mm (m. carpi ulneris, bipennate muscle) to 39.6 mm (m. flexor profundus caput radiale, unipennate muscle) in length. The myofibers of the leg muscles ranged from 10.0 mm (m. flexor superficialis, multipennate muscle) to 119.2 mm (m. soleus, fusiform muscle) in length. The ratio of myofiber length to muscle length in the fusiform muscle was higher than that in the uni-, bi-, and multipennate muscles.

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The muscles of the forelimb were functional-morphologically examined in a carcass of the aardvark (Orycteropus afer) that is highly adapted to the fossorial life and the digging behavior. The M. pronator quadratus, the M. abductor digiti I longus, the M. brachioradialis, the M. pronator teres and the M. supinator are well-developed. We suggest that the supinator-pronator movement by these muscles enables the aardvark to dig, crush and sweep the soils in its fossorial behavior. In addition, the M. digiti II runs obliquely to rotate the forearm around the ulna shaft. We think that this muscle may not only function as an of the digits II and III, but also as a supinator of the fore arm. Many muscles can be separated into two groups on the basis of their insertion. The M. digiti II and the M. carpi radialis insert to the digits-metacarpals II-III, whereas the M. lateralis and M. carpi ulnaris reach the digits-metacarpals IV-V. We suggest that the crushing of the soil is accomplished by the two medial digits and that the lateral two digits mainly act as a remover or a sweeper of the crushed soil.

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Summary: The indicis and the pollicis longus muscles differentiates from the profundus muscle. The indicis musde is an unstable muscle concerning its variations. Kosugi (1989) found the frequency of variations of this muscle to be 20% and described 18 different types of variations of this muscle. This study describes a rare case of the indicis muscle. The indicis muscle develops an accessory tendon in between the indicis and pollicis longus muscle. It passes under the retinaculum. At the level of 2nd metacarpal bone, the accessory indicis tendon is connected to the tendon of the pollicis longus muscle by a intertendinous connection.

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The peroneus tertius muscle was observed in five legs (2.9%) of three male specimens (3.4%) out of 174 legs of 87 (45 male and 42 female) crab-eating monkeys (Macaca fascicularis). They were all supplied by the deep peroneal nerve. Two types were observed in three legs of two specimens and grouped into Types III or IV and VIII or IX as classified by Kaneff (1980). These comprise a tendinous or a muscular expansion of the lateral compartment of the longus muscle. While the muscle observed in both feet of another specimen seems to correspond to the “so-called peroneus tertius” reported by Sommer (1907)and Preuschoft (1961) in gorillas.

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In domestic animals, the legs function in both postural maintenance and propulsion. The crural muscles participate in actions of the tarsal and toe joints. Mammalian skeletal muscles consist of myofibers, which are histochemically classified into three myofiber types, slow-twitch/oxidative (SO) or type I, fast-twitch/oxidative/glycolytic (FOG) or type IIA, and fast-twitch/glycolytic (FG) or type IIB myofibers. The histochemical characteristics of myofiber types reflect an aspect of function that myofibers possess. In the present study, we investigated the composition and average diameter of myofiber types of each muscle in crus of sheep and determined their roles in the movement of tarsal and toe joints. The tibialis cranialis muscle was a flat unipennate muscle and not capable to generate a large tension; however, it could function primarily in posture maintenance and play a cooperative role in adjusting standing posture. The flexor hallucis longus and flexor superficialis muscles were the major muscles that contributed to posture maintenance in leg musculature. These muscles were capable to generate a large tension and participate primarily in standing posture maintenance. The composition and diameter of myofiber types in ovine crural musculature reflected the role of each muscle in posture maintenance and locomotion.

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The “ habitus” phenomenon occurs in finger flexor tendon injuries and consists of a paradoxical extension of the interphalangeal joints after an attempt to flex the finger. The mechanism of extension is considered to be a contraction of the flexor profundus that is then transmitted via the lumbrical muscle structure to the expansion. Using electromyography, we recorded the lumbrical muscle activity during the paradoxical extension phenomenon to determine whether the lumbrical muscle contributed to this event. Two patterns of electromyographical activity of the lumbrical muscle were observed. Group I (6 fingers) displayed electrical activities in the lumbrical muscle during flexion tasks, while group II (12 fingers) did not. In group I, the lesions were mainly located in zone V, and the response to range of motion exercises was satisfactory. In group II, nearly all of the lesion were located in zone II, and half of the cases required additional surgical interventions. Group II appeared to exhibit the “ habitus” phenomenon, while group I exhibited an “ habitus-like phenomenon.” To distinguish between these two phenomena, an electromyographical examination of the lumbrical muscle must be performed.

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In order to determine whether the muscle bellies of the carpi radialis longus and brevis (including additional slips) show laminar disposition, they were observed in 490 upper limbs of 245 Japanese cadavers. The author examined them from the point of view of lamination of the muscle slips (bellies) and classified them into 22 types in this study.
The carpi radialis longus muscle consists of five layers (A, B, C, D and E). Their proximal portions are disposed from radial deep to ulnar superficial as A, B, C, D and E, and the distal portions from ulnar deep to radial superficial as A, B, C, D and E. C is the main part of the carpi radians longus muscle, and A, B, D and E are additional (accessory) slips. The main part (C) is inserted into the second metacarpal bone. A and B cross beneath the main part (C) to the ulnar side of the hand and are inserted into the third to second metacarpal bones. D and E pass across on the main part (C) to the radial side of the hand and are inserted into the second to first metacarpal bones.
The carpi radialis brevis consists of three layers (X, Y and Z). Their proximal portions are disposed from radial deep to ulnar superficial as X, Y and Z, and the distal portions from ulnar deep to radial superficial as X, Y and Z. Y is the main part of the carpi radialis brevis muscle, and X and Z are additional (accessory) slips. The main part (Y)is inserted into the third metacarpal bone. X passes deep to Y to the ulnar side of the hand and is inserted into the fourth or third metacarpal bone. Z passes superficial to Y to the radial side of the hand and is inserted into the third or second metacarpal bone.
The carpi radialis longus muscle showed the normal form (C only present) in 326 of 490 cases, and had the main part (C) and one to three additional slips (A, B, D, E) in 164. The carpi radialis brevis showed the normal form (Y only present) in 389, and had the main part (Y) and one or two accessory slips (X, Z) in 101 of 490 cases.

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Tinamids are small cursorial birds with limited flight ability. They are phylogenetically nested within a clade composed mostly of large, flightless birds (ratites). Their ability to fly and the evolution of flightlessness in the clade are currently not well understood, and this is largely due to a paucity of literature on the osteological and muscular anatomy of these birds.

Two Eudromia elegans (Palaeognathae: Tinamidae) were dissected and four skeletons were examined. The skeletons of Eudromia are characterized by a thin sternum, short and stout humeri, and developed lower limbs. Eudromia maintains some ancestral characters in the postcranial skeleton, such as elongated lateral trabeculae of the sternum, an absent rostral external spine of the sternum, and lack of fusion between the distal ilium and ischium. The lost of the hallux suggests cursorial adaptation occured not only in Strutioformes (Struthio has only two digits) but also even in tinamids. Accordingly, the muscles inserting on the hallux are lost or shifted to other digits. However, the body plan of Eudromia is quite similar to other modern volant birds, like Gallus.

Our specimens showed differences in musclular morphology from previous descriptions of tinamou anatomy, particularly, the absence of M. iliofemoralis internus and the femoral head of M. tibialis cranialis. We also compared Eudromia with other ratites, such as Struthio, Rhea, Apteryx, and Dromaius. In the shoulder girdle, Eudromia has a large M. pectoralis thoracica and M. supracoracoideus, which are used for the downstroke and upstroke, respectively, but these muscles do not have such antagonistic actions in other ratites due to differing origins and insertions. The morphological changes in the pelvic girdle are minor compared with those in shoulder and forelimb regions. Ratite have enlarged Mm. femorotibiales, and M. iliotorochantericus medius and M. ischiofemoralis are diminished in size, except in Apteryx. Eudromia has a thin M. caudofemoralis pars pelvica, while other ratites have lost M. caudofemoralis pars caudalis (in Dromaius and Rhea) or it is considerably diminished (in Struthio). The differences between Eudromia and other ratites we find are attributed to the retention of flight ability in Eudromia.

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In this study, we observed muscle activity of common digital muscle and flexer superficialis muscle in forearm with the multi-channel electromyography(EMG) measurement system using conductive fabric for research the mechanism of finger tremor. We compared up and down motion of laser pointer affixed to middle finger to muscle activity of common digital muscle and flexor superficialis muscle. As a result, common digital muscle move a few msec earlier if middle finger moved upward, and flexor superficialis muscle move a few msec earlier if middle finger downward.

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The two small stress proteins, HSP 27 and αB crystallin, are expressed widely in normal rat tissues and abundantly in skeletal muscle. In order to clarify the physiological significance of these stress proteins, the changes in their levels were determined immunochemically, in the slow-twitch soleus muscle and fast-twitch longus muscle or rectus femoris muscle of growing rats, and in those of adult rats during denervation and tenotomy. HSP27 was quantitated by specific immunoassay, similar to that for all crystallin, with antibodies raised in rabbits against purified rat HSP27. In adult rats, HSP27 was present at high levels in tissues composed of striated muscle, and it was present at much higher levels in the soleus muscle than in the rectus femoris or longus muscle, as is αB crystallin. However, in rats of perinatal age (from prenatal day 2 to postnatal day 3), levels of HSP27 in the rectus femoris muscle were enhanced like those in the soleus muscle, reaching the maximum levels at postnatal day 3. Thereafter HSP27 in the fast-twitch muscle showed a steep decrease. The increase in αB crystallin in the hindlimb muscles was also observed in the perinatal period. However, αB crystallin concentrations in the soleus muscle of perinatal rats were as low as those in rectus femoris muscle. The transection of the sciatic nerve resulted in decreases in the levels of HSP27 and αB crystallin in the soleus muscle of adult rats, together with increases in the levels of the two proteins in the longus muscle. The decrease in HSP27 and αB crystallin in the soleus muscle was also observed after tenotomy. However, there was no increase in the concentrations of the two proteins in the tenotomized longus muscle. These results suggest that the two small stress proteins in the hindlimb muscle, in particular HSP27, are induced by events associated with birth, and that the expression of HSP27 and αB crystallin in the skeletal muscles is controlled similarly in adult rats.

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The lumbrical and interosseous muscles in twenty-five feet of Japanese adult cadavers were dissected. The lumbrical muscles mainly continued into the dorsal aponeuroses or the terminal tendons of the longus muscle, though they occassionally issued some accessory and slender tendons inserting into the bases of the proximal phalanges. Rarely, the lumbrical muscle showed an atavistic anomaly. In this anomaly, the lumbrical muscle was divided into two tails which continued into the bases of the proximal phalanges of the contiguous toes. The plantar and dorsal interosseous muscles were mainly attached to the bases of the proximal phalanges. Frequently, the plantar and dorsal interosseous muscles issued some accessory and small tendons continuing into the dorsal aponeuroses. This fact suggests that the plantar and dorsal interosseous muscles in the foot, like the palmar and dorsal interosseous muscles in the hand, are composite muscles derived from the flexor brevis, contrahens and other muscles.

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We constructed an arm holder for muscle exercise from a forearm-shaped plastic shell and magnetic resonance (MR) imaging position markers and determined the echo time (39 ms) for T₂-weighted spin-echo MR imaging from T₂ values of the exercised (50 ms) and resting (32 ms) muscle at 0.2 tesla. The smallest detectable muscle was the digiti minimi muscle (cross-sectional area 25 mm²). This combination could be useful to monitor finger exercise in patients undergoing physical therapy.

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