Examination of the nerve supply in the palm was done on a total of 100 hands of 50 cadavers of adult Macacus cyclopsis.
The nerves supplying the palm are the terminat i o ns of the N. medianus and the N. ulnaris.
I. N. medianus
The N. med. passes beneath the middle part of the Lig. carpi transversum to the lower layer of the Aponeurosis palmaris. First, the Rr. musculares to the muscles of the ball of thumb are given off after which the remaining part separates into several branches to become the Nn. dig. pal. comm.. The latter further give rise to Rr. musculares to the Mm. lumbricales and then become the Nn. dig. pal. prop. which usually innervate the edge of fingers from the thumb to the ring finger.
1. Rr. musculare s to the muscles of the ball of thumb
From the N. dig. pal. comm. I, which is formed by the N. med. after it emerges in the palm, nerves to the muscles of the ball of thumb except the M. add. poll. brev. and caput profundum of the M. flex. poll. brev. are usually given off.
Also, cases in which the capu t profundum of the M. flex. poll. brev. is supplied by a R. musculares from the N. med. in addition to the R. prof. n. uln. for double innervation and abnormal cases in which the M. opponens pollicis is not supplied by the N. med. but compensated by the R. prof. n. uln. were seen at a considerable frequency.
2. Rr. musculares to the Mm. lumbricales
Usually, the M. lumbricales I is supplied by a branch from the N. dig. pal. prop.3 while the M. lumbricales II is innervated by the N. dig. pal. comm. II. However, cases in which the M. lumbricales III also is supplied only by a branch from the N. med. and cases in which it is innervated by the R. prof. n. uln. in addition to this nerve for double innervation are seen considerably frequently while cases in which the M. lumbricales IV is supplied only by the branch from the N. med. and cases in which this muscle receives double innervation by the R. prof. n. uln. are very few.
3. Nn. digitales palmares communes and Nn. digitales palmares proprii
The N. med. in the palm immediately separates into the Nn. dig. pal. comm, I-III, but these nerves, after giving off the above Rr. musculares, further separate to become the Nn. dig. pal. prop. which supply the edge of the each finger.
The pattern of distribution of these nerves may by classified into five types, but the most common type is that in which the nerve immediately separates into the N. dig. pal. prop.1 and the Nn. dig. pal. comm. I-III after which the latter further separate into two to supply both edge of the palmar side of the thumb, index finger and middle finger and the radial edge of the ring finger. This pattern is the most frequent type in the Japanese.
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