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Aesxual and Sexual Reproduction
tudinally along the dorsal middle (piṭṭha) of all chordate embryos and is formed at the same time as the mesoderm,2 ,21 Biology explains that "In all Vertebrates the notochord is short-lived structure, eventually replaced by the vertebral column",22
It seems from the absence of notochord with a proper nomenclture in Jaina Biology that the Jainacāryas did not mention it because it was a short-lived structure, eventually replaced by the vertebral column. Development of the Nervous System
Although the two week old human embryo is a simple arbuda21 (a simple solid ball of cells or a simple flat disc, according to Modern Biology,) the two month old embryo has nearly all its structure in rudimentary form.22 The brain (Sira or matthu) and the spinal cord are among the earliest organs to appear. It is stated in Jaina Biology that in the fifth month there develop fully the five pindas (two arms, two legs and head), 24 while siras, dhamanis (circulatory vessels) and Snayus (nerves) develop later on. According to Modern Biology, "All the regions of the brain are established by the fifth week of development, and a week or two later the outgrowths which will form the large cerebral hemispheres begin to grow,"25
Development of Body Form:
The conversion of the two-week old flat disc (arbuda) into a roughly cylindrical embryo is accomplished by three processes. (a) the growth of the embryonic disc into pesi (blocks of muscles-mamsakhaṇḍarupa),26 (b) the underfolding of the embryonic disc, especially at the front and rear ends into ghana (sama caturasraṁ māṁsakhaṇḍam bhavati - square-shaped blocks of muscles)27 and (c) the construction of the Ventral body wall to form the further umbilical (nābhi).28
21. Biology, p. 437
22. Biology, p. 437. Tandula Veyaliya, 16, p. 35.
23. Tandula Veyaliya, 2, p. 6.
241
25. Tandula Veyaliya 2 p. 6.
26. Biology p. 447.
27. "Sattaeṁ kalalam hoim. sattaham, hoi abbhuyam (
abbuya jayae pesi, pesio, ya ghanam bhave //', Tandula Veyaliya 2, p. 6.
28. Ibid.
JB-31
24. Ibid. "Bie mase pesi saṁjāya ghaṇā" 2
It suggests that the two-month old embryo has nearly all its structure in rudimentatry form.
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