日本人胎児の腰仙骨神軽叢に就て

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The material consists of 120 sides of 60 Japanese fetus from 5 to 10 months old. These 120 specimens were classified after the participating roots of the spinal nerves in 15 forms and 5 types (I-V).In the II and III types, which occur together in 83.3% and may be called normal, the plexus consists of Rr. anteriores of Th12, -S3, (II, 32.5%) or L1, -S3 (X, 50.7%). In the type IV (5.0%) and V (8.3%) are the roots of the plexus shifted caudal so that S, gives the share for the formation of the plexus, while in the type I (3.8%) cranial so that the most caudal root of the plexus is S2.According to the forms of N. femoralis and ischiadicus which are the main parts of the plexus the type II is classified in 5 (a, b, c, d, e), III in 4 (a, b, c, d), IV in 2 (a, b), and V in 3 (a, b, c).(Fig 1-13)In animals the form of the plexus lumbosacralis is very simple, among them the mammals have the most complex forms which resemble to the man's plexus. In our 120 specimens there are 17 more simple and 22 more complex forms.Among our specimens there are 2 the most primitive forms of the brachial plexus, 7 more primitive inclined. In the former 2 the lumbosacral plexus is a little simple and primitive in one specimen, while in the other not simple, but a little more complex, in the latter 7 one is simple, 2 is complex while the other 4 specimens normal.(Fig.14, 15) So there is no intimate correlation between Plexus brachialis and lumbosacralis in the phylogenetic primitiveness.After the frequency of the furcal nerve (Jhering) which occurs in L4 (82.5%) or L5 (17.5%) there is no difference between our Japanese and German (Eisler) or English (Paterson).(Table 4) In our one example of type V form c there is no furcal, no lumbosacral trunk.(Fig. 10)When our specimens are arranged after Bardeen and Elting the most frequent form d. i. median origin occurs in 57.5%, the proximal origin in 24.1%, distal origin in 18.3%, while in case of the American white 36.5, 47.3 and 16.2 respectively.There is no specimen of N. obturatorius accessorius, which occurs a little frequent in European.The difference of form of the plexus between right and left is very slight so that the shifting of one complete segment in one side does not occur.