2265. The principal function of the vessel is that of secretion, whereby nutrition is imparted. This secretion must take place in the whole body, in so far as it is opposed to the lung. The vessels then pass over into the finest canals, and are called capillary vessels.
2266. The capillary system of vessels is an organ in antagonism to the lung; what enters the latter organ, passes out through the former.
2267. The capillary system of vessels is the property of the tegumentary system. It may almost be said that wherever there is integument, there capillary vessels are present. The most perfect evolution of capillaries is the integument. It is the proper exsecernent, in opposition to the intestine, which is the absorbent organ.
2268. Evaporation is the essential tegumentary process.
2269. The product of the evaporation is mucus.
2270. In the evaporation, however, the mucus becomes analyzed by the influence of the air and light.
Epidermis.
2271. The external mucus exuding from the skin becomes oxydized, the inferior on the contrary reduced; the oxydized becomes vitreous and transparent. It is the Epidermis.
2272. With the maximum of oxydation the epidermis passes over into a vitreous transparent horn, e. g. scales.
2273. The scales, which invest the toes and digits are called claws, and finally become nails. The finger-nail is nothing but a scale, which in this situation has become particularly large and strong.